How can a non-Catholic get into state of grace as understood by the Catholic Church?

State of grace: > Condition of a person who is free from mortal sin and pleasing to God. > It is the state of being in God's friendship and the necessary > condition of the soul at death in order to attain heaven. source Now, > We cannot merit anything supernatural if we are not in a state of > grace. To argue the contrary is to argue for Pelagianism . > Nonetheless, God does hear the prayer of the repentant sinner. > > ... but the prayer of the unrepentant sinner, who prays for something > other than for the graces of conversion, is a prayer lacking in merit > or efficacy it would appear. source I know some Protestants who are sincere in their faith and I saw them deeply praying. But from the quote above I also know that even if they pray deeply they can't merit anything as they aren't in a state of grace because they are not taking part in God's divine nature according to some theologians and the Catholic teaching . My question is, how can a non-Catholic obtain the state of grace as understood by the Catholic Church? Is it even possible without becoming a Catholic? Does it even make sense for a non-Catholic to pray for anything other than for a conversion to become a Catholic?