This question was asked in the Building Catholic Men Twitter group.
I would encourage him to find a regular confessor to whom he could be accountable. Regular frequent confession, frequent reception of the Holy Eucharist, and the daily Rosary will help anyone kick the pornography habit or any other sinful behavior. You can crucify your flesh, but only with God’s help and the grace flowing from the Church. God bless you!
I would encourage him to delete all apps that he uses to access these things. If he is Married, suggest he go to bed the same time as his Wife. I would recommend he use accountability software (Covenant Eyes, etc.) Offer to go with him to the Sacrament of Reconciliation.
As with any sinful behavior, he can ask the Lord to change his mind and body so that he is no longer interested in such things.