I had come out to my girlfriend of one year while listening to Howard Stern. He was saying how he'd like to put Kathy Lee Gifford in one. While listening to it my gf jokingly said something about me putting them on her. I responded that I would and she shockingly said "really" My heart started pounding and I said, "I have something to tell you" and the rest is history.
So my advice: perhaps find a clip of a talk show or something that involves diaper wearing and try to find a way to have it "randomly" come on to inspire some conversation.