Teaching adult community choir to use solfège: what are your suggestions for effective, efficient teaching that keeps the joy and dedication in singing with the choir?

People join community choirs as adults for several reasons, and I’ve found that learning a new pedagogical language like solfège is not very high among them. But I want to help singers gain confidence, independence, and skill, so I’m looking for tiny, every-rehearsal steps to enable them to use this practice. But I want to keep the joy, passion, dedication, and transcendence in rehearsals, too. What has worked for you?