I tend to use miniatures paints thinned with rubbing alcohol. If you're starting with a versatile plastic you'll want to do many, many thin coats, let the nylon really drink in the color, and let them dry thoroughly between coats, especially the first few. It will look patchy to start, that's normal. After several coats you'll get a smoother surface less prone to bleed, and you can start in on details.
For detail plastic, I recommend priming and then painting in thin coats.