I use Model Masters acrylic, mainly flat color for interor. I use simple water for thinning.
btw Don't use Lacquer paint or thinner with this airbrush !!! I had that airbrush before too (a320) and it died after 2 or 3 use of lacquer paint. Instruction clairly say that
this airbrush is for Acrylic ONLY. Don't do the same error as me. It's not a very bad airbrush, but it's very limited for paint.
btw, here is
a good read