What is the best devotion to help the souls in purgatory?
1. The holy sacrifice of the Mass is the chief source of devotion for the holy souls.The most
powerful means to relieve or release a soul from purgatory is through the Holy Sacrifice of the Mass. You’ll find that in the Catechism. It says it in 1032: “From the beginning, the Church has honored the memory of the dead and offered prayers in suffrage for them, above all the Eucharistic sacrifice, so that, thus purified, they may attain the beatific vision of God.”
2. After the Mass, the next most powerful way to help the souls is the Rosary, the most powerful
Marian prayer on earth — in her approved apparitions, Mary says pray the Rosary for peace in the
world, in your hearts, in your family — and the Stations of the Cross, Divine Chaplet, because they’re indulgences.
You have to be in the state of grace to help the souls in purgatory.