Forced feminization hypnosis is another method of making your man do exactly what you want. Why not transform your submissive into the ultimate part time girl. With hypnosis he can be hypnotized into hallucinating that he is indeed a woman. You can have him feeling his breast and vagina and actually seeing a woman when he is looking in the mirror.
This can be combined with regression therapy to convince him that he is and always has been a woman. Hypnosis can also go so far as to leave him with vivid experiences of having had sex as a woman. By using this therapy you can transform your man into a woman and then back into a man using a set of keywords. You can also have it so that he can have no memory of his alternate self or the things he has been doing. Of course you can also have it so he remembers everything.