Here's a few PMC links. I'm pretty sure there are message boards out there devoted to PMC too...have to hunt around. Or maybe someone here can direct you to a message board site...but there is a more specific section here on LE for you PMC questions too...
http://www.lampworketc.com/forums/forumdisplay.php?f=22
http://www.silversmithing.com/1clay.htm
http://jewelrymaking.about.com/library/blmeclay.htm
http://amazon.com/s/ref=nb_ss_gw/002...Go.x=8&Go.y=10
Good luck!
Lil