I recently sprayed my mouse, CD bezel and Floopy drive bezel black and i stole my nephews can of black primer that they use for painting models. It is only primer and shouldnt be used as paint but it looks great (nice matt black finish). Used some matt spray on varnish and they all look pretty proffession.
As it was primer as well i didnt have to play around sanding any thing down, just gave all the parts a good cleaning with Alochol (trusty old tape head cleaner) let them dry and sprayed away, did 3 coats of paint and 4 coats of varnish. Trick is to do a very light coat, let it COMPLETELY dry and do another one and just gradually build it up.
Like i said the paint and varnish i used was games workshop stuff, only used it because it was to hand but apprently you can get different varnish types (gloss, matt and extra tough) and different colours of primer. The main thing is they are all plastic safe to so you dont have to worry about your plastic bits melting as you paint them.
If i was doing a larger surface i would have done a lot more prep work but for the little bits i did this took maybe 2 hours (including drying time) and turned out much better then i expected.