"Please tell me how you use self-hypnosis to support a fast!"
It is very simple Lauray, and in fact I think it would be one of the best things you could do even if you never fasted. Why?, because from reading your posts you seem to have a lot going on in your life, and one of the main ingredients of SH is to practice relaxing, and letting go of the everyday commotion that we all have in our waking conscious time.
As for SH, as it relates to fasting, the idea is to get to this relaxed state where your subconcious resides, and reprogram your thoughts, and habits to do whatever it is that you want to do.
The subconcious mind is where all your habits, and ways of thinking are that dictate how you act, and what you have learned to be the course of action for you.
You do this by suggestions, and visualization after you get into this relaxed state of self hypnosis. I'm not a teacher of SH, so I suggest you get some books on the subject. I started out learning SH in the 60's, and 70's so the books might be out of print. Here are a few in case.
Psycho Cybernetics by Maxwell Maltz. visualizations
The power of your subconscious mind by Dr. Joseph Murphy
Self Hypnosis by Laurance Sparks
I think learning the mechanics behind SH is important, but to somebody that wanted to speed the learning process, I would go with an audio version that you can purchase very cheap that will do what you need. Here's one I ran across that you can try before you buy. I tried it, and it works well. It differs from my own approach in that it is longer in length, but I have been doing it for so long that I can do short cuts to arrive at the same place. I can tell you that this is the real thing, and all you have to do is practice this an a continual basis, and you will get where you want to go.
http://tinyurl.com/yv4495
Read the links on this page for explanations of "How to" also.
Good luck