Upvote:2
First, you must understand what the RCC teach about grace. Here.
2002
God's free initiative demands man's free response, for God has created man in his image by conferring on him, along with freedom, the power to know him and love him. The soul only enters freely into the communion of love. God immediately touches and directly moves the heart of man...
Following this quote, if a person never responses he might need help from other's prayer. Through the other's intercessions, God can grant him many other opportunities where he can response. God will not violate man's free will and won't force him to response. If a man won't response God can't immediately touches and directly moves the heart of man.
You are saying
Does this mean that God preconditions His aid for sinners on other people's prayers?
Yes and no. First of all, God gives enough and sufficient opportunities to every man for his conversation. If a person runs out and fails to answer God's calling then other's prayers and sacrifices can bring more and new opportunities.