Primarily, I use acrylic paints. Most any acrylics will work fine, be they the $.99 specials or the high-end professional series. Acrylics mix easily, dry quickly, and react well with primer.
Primarily, I use the Ceramcoat brand of acryclics, commonly found in craft stores. I’ve used these since I was a kid. I know some customizers who swear a decent custom cannot be painted with these kinds of acrylics. I feel this site is a testament to the contrary, as everything you see was painted with the “cheap” paints.
Many customizers now prefer the more expensive “Acryl” brand by Testors. I’ve dabbled in these, and found them to be fine paints. But there’s nothing I can do with Acryl that I can’t do with Ceramcoat cheaper.