Hey Tom,
I don't know if it's the "right" thing to do, but I hate having holes where they don't belong, so I rarely just shrink the circle of cps together. Instead I join them to make new patches and close it off. That's another way to solve you foot problem.
While I don't know how it works, porcelain is supposed to be the best way to smoothe things out. I believe there is a tutorial on it's use at the resource matrix, or if not I bet someone has a link to the tut handy and could post it.
As for making it plasticy... sorry, I have no idea on that one.
Good luck,
Mal