“Jesus, have mercy on the Souls in Purgatory and the Souls on Earth” is one prayer, I say it after every ending Sign of the Cross.
The Prayer of St. Gertrude is for the Holy Souls. I say it at the end of every Divine Mercy chaplet. You can also say the St. Gertrude’s prayer over and over as a chaplet. There are Youtube directions on how to do this.
There are special Rosaries for the Holy Souls that you can find online (some are 5 decades long and some are 6 decades long), and a Litany for the Holy Souls that you can find online also.
I also give all my indulgences to the Holy Souls. For partial indulgences this happens via my Marian consecration. For plenary indulgences I make a list with a particular soul for each one and ask Mary to please give the plenary to the designated holy soul.
