What my wife did was tell me not to do anything to stop or delay cumming. She said to cum as fast as I could, and not keep stopping to hold back because she didn't enjoy the constant interruptions. Mixed with denial, I was always ready to cum immediately. In no time I became really fast, and my wife never complained, instead started saying things that made me cum even faster. As the denial times became multiple months, and I became even faster, to the point I was starting to cum on the first stroke going in every time.
Her next step was to hold me outside her pussy, and have me fuck her hand without any penetration. The humiliation of being stopped from entering would make me cum before getting inside at all. After she did that for a while, she started giving me hand jobs only. I've been pussy-free now for 17 months and counting.