Most efficient (timewise) meditation techniques to experience joy and bliss?

Try "Entering the Jhanas" guide by Leigh Brasington.

Entering the first Jhana, confers piti (glee or rapture) and sukha (joy or happiness).

This guide may provide a timewise efficient way from the perspective of the trainer, to enter the first Jhana.

However, if you have problems with this, you may need to spend more time developing virtues (sila) first.

Buddhism is about non-attachment. The more we are attached to bliss, the more there is no bliss. The more we look for bliss, the more bliss cannot be found.

Practice renunciation.

In my opinion, the fastest method to achieve bliss is the first Jhana meditation, which is essentially a form of autogenic training. In this meditation, you review your progress in Dharma with regards to your Sila (ethics) and Prajna (understanding), and congratulate yourself on your achievements. You also congratulate yourself on the fact that you have actually managed to stop cycling through bad karma and accumulated enough good karma to the point when you can finally enjoy the peace of sitting in meditation, as opposed to endlessly chasing all kinds of samsaric goals. As you thus congratulate yourself, joy and bliss are generated.

Another type of meditation that can help with joy and bliss is Satipatthana. In Satipatthana you sit and feel your body, breathing, emotions, thoughts, and the overall state of everything - and make a conscious effort to relax and "gladden" all that. You do that by letting go of all negative stuff you're holding on to, and by simply generating a sense of enjoyment. As you do that successfully, joy and bliss are generated.

Another type of meditation that can lead to the same result, is Tibetan Yidam Generation meditation. In this meditation you sit down and convince yourself that you are an actual embodiment of a spirit or deity. Practically speaking, you can use any image you want, it doesn't even have to be a Buddhist deity. You can imagine yourself to be a reincarnation of Einstein if that's what works for you. If you find it hard to convince yourself that you actually are the deity, you make up some kind of ritual to invite the deity within yourself. The exact details don't matter, what matters is that you have to convince your subconscious that you are the deity. In some schools they go as far as to re-imagine the entire process of your birth and growth as that of a deity. As you do this, the emotional/mental traumas and obstacles that you have are purified, leading to experiences of joy and bliss.

Another meditation that can lead to joy and bliss, is meditation on chakras and channels. This is primarily an exercise at visualization. In this meditation you imagine all kinds of colors, energies, and symbols going through the psychosomatically significant spots of your body-image, which again serves to purify the emotional obscurations and lead to an experience of joy and bliss.

Joy and bliss arise when the five hindrances (desire, ill-will, sloth-and-torpor, restlessness-and-worry, and doubt) subside.

The desire for joy and bliss falls under the first hindrance. So whatever is the fastest technique to make you forget that you're seeking bliss... that's the fastest technique for seeking bliss :)

Subduing the five hindrances is the "first stop" for all meditation techniques, whether it is breath-counting, breath-following, metta, noting, or devotional practices. Different people respond in different ways to each of these. So try them all out and see which one motivates you to stick with it- that will be the best.

Two warnings:

(1) Joy and bliss are conditioned states, so they can disappear as quickly as they arise, especially early in your practice (and "early" may mean years). If joy / bliss fades, or doesn't last past the sitting time, it isn't a failure. It's the natural passing away of all conditioned states.

(2) Not everybody experiences joy and bliss when the hindrances subside. Some people, particularly those with a trauma history (though nobody knows for certain why), may experience disturbing imagery or emotions. If this happens, be careful about pushing your technique too hard. Some Buddhists will insist that it is a sign that you are not meditating hard enough. Be wary of this kind of advice. Not all problems are solved by meditation, and other kinds of work may be necessary too.