I'm thinking of getting me some polyester resin (normally only use epoxy) for playing with some small moulds and parts (non structural). I already have powder bound csm for use with epoxy - does polyester work ok with this or would I be better getting some emulsion bound?

Powder bound CSM works fine with polyester, so if you already have some then give it a go. Personally I don't particularly like the stuff, I find it a bit harder to work with than emulsion bound strand matt.