Munnys are a really good product, give them a good scrub with some soppy water and they'll take pretty much whatever medium you wanna use on them.

I've used a couple of different clays on them.

firstly i used a two part clay called milliput (use the ultra fine one used for doll making) which is good but only gives you a small window for working before it sets.

Second time round tried fimo which is oven setting, although easier to mould can be risky putting munny in oven as they do get very soft and if there is a lot of weight in clay on them can even cave in, also is brittle once fired

as for painting dont think you can go wrong with games workshops range of citadel paints they're accrylics and give you the same finish on most materials

have fun mate they're wicked to do, got another standard blank and two minis left on my shelf to custom!!