can relate to the feeling hopeless about the shy bowel desensitisation. like you, i have shy bladder as well, and have done extensive desense work a la steve soifer style workshops and buddying up with other sufferers. and my shy bladder is a lot better (though i still have it).
when i first set up this site 4/5 years ago, steve soifer suggested i write a book on the condition but i felt i couldn't for exactly the reasons you outline above. what's the point of writing a book explaining what your problem is but offering no hope of improvement?
over the years though, my shy bowel has improved a lot (though i definitely still have it as a condition the same as shy bladder). so, having got better around shitting near others, i've written the book steve suggested i write four years ago.
john the webmaster has put up a downloadable pdf of the first chapter of the book which includes the contents page if you wanna get a taster of it. the text button is on the book page.