What is Mastery of reflectionJhana mastery

These five powers have to be mastered, DeusIIXII, for the purpose to develop right view, for the purpose to gain proper concentraion, for the purpose of release:

(the) first

❋ Namo tassa bhagavato arahato sammā-sambuddhassa ❋

There are these five strengths for one in training. Which five? Strength of conviction, strength of conscience, strength of concern, strength of persistence, & strength of discernment.

And what is strength of conviction? ...Vitthara Sutta: (Strengths) in Detail

Since certain prerequisites are possible missing, for one living at home: Development of the first six recollections/reflections can be done "no" matter how busy you are, if the busy is according to the Dhamma: AN 11.13

Since lack of stinginess is prerequisiten

"Without abandoning these five qualities, one is incapable of entering & remaining in the second jhana... the third jhana... the fourth jhana; incapable of realizing the fruit of stream-entry... the fruit of once-returning... the fruit of non-returning... arahantship. Which five? Stinginess as to one's monastery [lodgings], stinginess as to one's family [of supporters], stinginess as to one's gains, stinginess as to one's status, and ingratitude. Without abandoning these five qualities, one is incapable of entering & remaining in the second jhana... the third jhana... the fourth jhana; one is incapable realizing the fruit of stream-entry... the fruit of once-returning... the fruit of non-returning... arahantship.

Macchariya Suttas: Stinginess

Lack of Macchariya is reached by entering the stream. So as long difficulty in devotion, gratitude, precepts, e.g. having not really get known the Dhamma by proper attention, no right view yet, it's good to focus on the base. Then it might be possible, like for this generous and devoted man, to take on: fear & animosity are stilled

Much joyful effort is wished!

Addition, since just coming aware again: There is a "new" book, a gift of Dhamma to give, surely very usefullin this regard:

The Five Faculties : Putting Wisdom in Charge of the Mind, by Ṭhānissaro Bhikkhu. (revised October 22, 2017) In May of 2017, members of Le Refuge, a Buddhist group located near Marseilles, invited me to lead an nine-day retreat on the topic of the five faculties (indrīya): conviction, persistence, mindfulness, concentration, and discernment. These are a set of qualities that the Buddha numbered among his most important teachings. When put in charge of the mind, they lead all the way to awakening. Taken together, they deal primarily with the practice of meditation, which makes them a good framework for a meditation retreat. However, the first faculty—conviction—focuses on questions of self and world: what kinds of happiness you believe you are capable of attaining, along with what kind of happiness you believe can be found in the world. This means that the five faculties also provide an excellent framework for covering the entire practice of the Buddha’s teachings, both on retreat and in the world at large. (Source)

Note that "reflection", which you used in the question, is actually wisdom/"knowing" (paññā), or discrimination, such as reflection requires sati (mindfullness) and paññā.

Since knowledge at first place, having hear/read the good Dhamma, this might be most usefull to fullfil the answers demand on it's root.

[Note: This is a gift of Dhamma, not meant for commercial purpose and other low wordily gains by means of trade and exchange]

You should ask your jhāna-attained teacher.

5 mastery are:

1. āvajjanavasī - professional & quick & easy recalling 5 jhāna-factors, everytime everywhere.
2. samāpajjanavasī - professional & quick & easy to begin attaining jhāna, everytime everywhere.
3. adhiṭṭhānavasī - professional controlling time period of jhāna attaining, such as I just attaining a second then use actually a second, I just attaining a minute then use actually a minute, etc.
4. vuṭṭhānavasī - professional stopping the attaining jhāna.
5. paccavekkhaṇavasī = āvajjanavasī.

Paccavekkhaṇavasī is āvajjanavasī, nothing difference of them.

Samāpajjanavasī expert begin jhāna.

Adhiṭṭhānavasī expert attaining jhāna.

Vuṭṭhānavasī expert stop jhāna.

Path of purification page 146-148 [204-206 by e-book's auto number]:

131. Therefore he should acquire mastery in the five ways first of all with respect to the first jhána. Herein, these are the five kinds of mastery: mastery in adverting, mastery in attaining, mastery in resolving (steadying the duration), mastery in emerging, and mastery in reviewing. “He adverts to the first jhána where, when, and for as long as, he wishes; he has no difficulty in adverting; thus it is mastery in adverting. He attains the first jhána where ... he has no difficulty in attaining; thus it is mastery in attaining” (Paþis I 100), and all the rest should be quoted in detail (XXIII.27).
132. The explanation of the meaning here is this. When he emerges from the first jhána and first of all adverts to the applied thought, then, next to the adverting that arose interrupting the life-continuum, either four or five impulsions impel with that applied thought as their object. Then there are two life-continuum [consciousnesses]. Then there is adverting with the sustained thought as its object and followed by impulsions in the way just stated. When he is able to prolong his conscious process uninterruptedly in this way with the five jhána factors, then his mastery of adverting is successful. But this mastery is found at its acme of perfection in the Blessed One’s Twin Marvel (Paþis I 125), or for others on the aforesaid occasions. There is no quicker mastery in adverting than that.
133. The venerable Mahá-Moggallána’s ability to enter upon jhána quickly, as in the taming of the royal nága-serpent Nandopananda (XII.106f.), is called mastery in attaining.
134. Ability to remain in jhána for a moment consisting in exactly a finger- snap or exactly ten finger-snaps is called mastery in resolving (steadying the duration). Ability to emerge quickly in the same way is called mastery in emerging.
135. The story of the Elder Buddharakkhita may be told in order to illustrate both these last. [155] Eight years after his admission to the Community that elder was sitting in the midst of thirty thousand bhikkhus possessed of supernormal powers who had gathered to attend upon the sickness of the Elder Mahá- Rohanagutta at Therambatthala. He saw a royal supaóóa (bird) swooping down from the sky intending to seize an attendant royal nága-serpent as he was getting rice-gruel accepted for the elder. The Elder Buddharakkhita created a rock meanwhile, and seizing the royal nága by the arm, he pushed him inside it. The royal supaóóa gave the rock a blow and made off. The senior elder remarked: “Friends, if Rakkhita had not been there, we should all have been put to shame.”
136. Mastery in reviewing is described in the same way as mastery in adverting; for the reviewing impulsions are in fact those next to the adverting mentioned there (§132).
137. When he has once acquired mastery in these five ways, then on emerging from the now familiar first jhána he can regard the flaws in it in this way: “This attainment is threatened by the nearness of the hindrances, and its factors are weakened by the grossness of the applied and sustained thought.” He can bring the second jhána to mind as quieter and so end his attachment to the first jhána and set about doing what is needed for attaining the second.
138. When he has emerged from the first jhána, applied and sustained thought appear gross to him as he reviews the jhána factors with mindfulness and full awareness, while happiness and bliss and unification of mind appear peaceful. Then, as he brings that same sign to mind as “earth, earth” again and again with the purpose of abandoning the gross factors and obtaining the peaceful factors, [knowing] “now the second jhána will arise,” there arises in him mind-door adverting with that same earth kasióa as its object, interrupting the life-continuum. After that, either four or five impulsions impel on that same object, the last one of which is an impulsion of the fine-material sphere belonging to the second jhána. The rest are of the sense sphere of the kinds already stated (§74).

cr. www.accesstoinsight.org/lib/authors/nanamoli/PathofPurification2011.pdf