Nice neat paint jobs start with restraint. Don't stick all the bits together than then try to paint them, splash the colour while they are still on the sprue. Then let them dry. Be careful with the glue when you do begin assembly too.
Anyway, chassis bits are painted with Humbrol matt black using a brush. This is normally a good brushing paint and so it proved again with a single coat providing excellent coverage with not a hint of brush mark to be seen.
For variety, the exhaust system is covered in Mr Hobby (a Japanese paint so appropriate) Dark Iron. This stuff prefers spraying but if beaten with a Tamya paint stirrer will condescend to brush. It's an odd colour, not black or dark grey and slightly shiny. Not sure really, but it's underneath so doesn't really matter. I can see uses elsewhere though so a handy test.
Bodywork should be baby blue, or invalid blue as it's called when applied to Volkswagens. I didn't know this when I started so used a pot of Humbrol 157 - Azure blue. To be fair, I'm not wildly out as the appeal of this pot was that the one thing is isn't is Azure blue. More a pale blue/mauve colour. Pretty but nothing like a pair of denim jeans, which is what I hoped to paint when I bought it...
Anyway, the body was sprayed along with some interior parts. Only after I'd done this did I realise that there is no positive fixing for the wing mirrors so they had to be fitted with superglue. And I got one in the wrong place and had to polish away the glue before touching up with thinned paint and a brush. I don't think you can tell.
I still like the colour though.