Mr. Musick, 37, wore a faded T-shirt and blue jeans and had mussed hair and a soul patch beneath his lower lip. Instead of his weekly sermon, he directed the congregants to make their way among three makeshift altars, each with a stack of cards carrying a prayer and a list of topics to think about.

"You're going to be put in a position where you have to think about your relationship with God," Mr. Musick said.