I'm so glad it worked out for you~!
1. Just a pair of plain black clogs. They had sort of a leather-type texture to them, and the Model Magic stuck to them pretty easily. In places where it didn't stick, I just secured it with hot glue.
2. Hrm, that sounds weird... All I did to mine was sand it as soon as it was dry. Is the batch of Model Magic you used old or new? Because as it sits over time (even if it's not opened) it can get that sort of "gritty" texture to it.