I have a good friend whose ministry I've been supporting for nearly a decade, rather specifically as directed by the Holy Spirit.
He is something of an undercover evangelist (along with his wife) in a strict Muslim country. He's operating as a building contractor, and he is that. He does not preach, he does not try to build a congregation. But he also demonstrates by his daily walk, within the boundaries of what's legal in that country, that he's a Christian.
Every so often, a Muslim man will come to him in private and say something to the effect of, "I have seen that you are a very devout Christian. Teach me about Jesus."
("No man can come to me, except the Father which hath sent me draw him..." John 6)
So then, my friend will begin privately meeting regularly with that man to read the scriptures. No preaching, no doctrine-pounding, just reading the scriptures. Just reading. He may answer some questions, but mainly he lets scripture speak for itself. They will, over the course of time, go through the four gospels, then Acts, then Romans. At the end of Romans, my friend will simply ask, "What do you think of all this?"
He reports that 100% of the time, if the Muslim has stuck with him through those books, the man will say, "I believe this. I want to be baptized." And like the Philippian jailer and Cornelius, he will have his family baptized with him.