Damn snow. I'm getting all antsy about all the places I want to go. Thinking of Minch Cave, and I do a simple search to see you actually went in. Anyway, I learned A self belaying technique during the Summer for climbing trees. It's described pretty well on this site:
http://www.climbingarborist.com/footlocking.html
I haven't tried any of the other techniques on the site, but I'd love to work them out sometime. I was thinking it would be the perfect set of tools for getting into deep holes, and you could practice the technique on just simple trees until your comfortable enough to trust your escape on the technique. Until the snow melts I'm just twiddling my thumbs with too many things on my list to try.