I once gave the advice to my then MTF girlfriend to put some local oral anaesthetica on her d*ck before sex, one of those you can get at the pharmacy without a prescription if your teeth hurt or you have an infection in your mouth. She was amazed as after about 10 minutes, she could not feel anything there for about an hour and as far as I remember, she also told me no erections whatsoever so sex was kind of relaxing for her that time (I just went down to her breasts and kept away from the risky parts until she came). Of course, don't use that stuff too often, read the instructions first, don't use too much of it and first try it somewhere else as some people are allergic to it. Oh, and if you put a condom on first, the numbing effect stays longer.