You need a solvent to smooth. I got some isopropanol from ebay. You can get it almost pure which is good for knocking back very rough areas, to 70% which is good for more delicate areas such as skin texture. You can also sand the sculpey with fine grit paper after it's been baked to get a super smooth surface.
As for painting, I see you are in the UK, so first grab a can of Halford's grey or white primer and give it a fine coat, then paint with acrylics of your choice really, from the standard art supply type to the more expensive kinds.
Oh, and let's have a look
Al