As far as a 12-step program, I think the graduated exposure therapy (classical conditioning like in John Watson's experiment with baby Albert, if you've ever taken a psychology class) presented in this book I have about paruresis may in fact work for parcopresis, too. It will probably be more difficult to control the situations in which you therapize (peeing is easier: if you stand at or sit on the toilet long enough in silence, you'll be able to go whether you initially felt an urge or not; this is not the case with parcopresis, as I'm sure you all know), but if you work at it, I think it will work. There's no mind tricking involved. It simply involves easing your brain into understanding that pooping is okay to do.