The Rosary or Chaplet for the Souls in Purgatory is a practice earnestly recommended to all persons who desire to assist the Poor Souls.  It is said on any ordinary beads.

Psalm 129.  De profundis

Out of the depths have I cried unto Thee, O Lord; * Lord, hear my voice.
2  Let thine ears be attentive * to the voice of my supplication.
3  If thou, O Lord, shalt observe our iniquities , * O Lord, who shall endure it?
4  For with thee there is merciful forgiveness; * and by reason of Thy law, I have waited for Thee, O Lord.
5  My soul hath relied on His word: * my soul hath hoped in the Lord.
6  From the morning watch even until night, * let Israel hope in the Lord.
7  Because with the Lord there is mercy, * and with Him plentiful redemption.
8  And he shall redeem Israel * from all his iniquities.

Or Pater and Ave

Our Father, who art in heaven, Hallowed be thy Name.  Thy Kingdom come.  Thy will be done, On earth as it is in heaven.  Give us this day our daily bread.  And forgive us our trespasses, As we forgive them that trespass against us.  And lead us not into temptation, But deliver us from evil.  Amen.

Hail, Mary, full of grace, the Lord is with thee : Blessed art thou among women, and blessed is the fruit of thy womb, Jesus.  Holy Mary, Mother of God, pray for us sinners ; Now, and at the hour of our death.  Amen.

V.  Eternal rest grant unto them, O Lord.
R.  And let perpetual light shine upon them.

Act of Faith
My God, I believe in Thee, because Thou art Truth itself;
I firmly believe the truths revealed to the Church.

Act of Hope
My God, I hope in Thee, because Thou art infinitely good.

Act of Charity
My God, I love Thee with all my heart, and above all things, because Thou art infinitely perfect; and I love my neighbour as myself, for the love of Thee.

(Indulgence 7 years, 7 quarantines, each time.  Benedict XIV, Jan. 28, 1756.
Plenary once a month, if said every day.  Benedict XIII, Jan. 15, 1728)

(Plenary, in articulo mortis (at the point of death) if frequently used during life.
Benedict XIV, Jan. 28, 1756)

Sweet Heart of Jesus, be my love.

(300 days once a day.  Leo XIII, May 21, 1892)

Sweet Heart of Mary, be my salvation.

(300 days each time.  Pius IX, Sept. 30, 1852)

Jesus, meek and humble of heart, make my heart like unto Thine.

(300 days each time.  St. Pius X, Br. July 9, 1904)

St. Joseph, model and patron of those who love the Sacred Heart of Jesus, pray for us.

(100 days once a day.  Leo XIII, Dec. 19, 1891)