Dear St John Bosco,
In need of special help, I appeal with confidence to you, for I require not only spiritual graces, but also temporal ones, and in particular for... (here mention your intentions).
May you who on earth had such devotion to Jesus in the Blessed Sacrament and to Mary Help of Christians, and who always had compassion to those who were suffering, obtain from Jesus and His heavenly mother the grace for which I now pray. I also ask for a sincere resignation to the will of God. Amen.
Offer an Our Father, a Hail Mary and a Glory Be.