It took me some trial and error to come up with a decent technique. I work with acrylic paints (Tamiya) because they clean up easy and Model Master is a brand many swear by. If your local hobby shop has a Tamiya rack, it probably has some Tamiya brushes. Try their fine brush. I use it for my itty-bitty work and I've never cussed using that brush. I think I dropped $8 on it, but it's still as good as new one year later.
Stir before using for best results. If the bottle of paint starts to get glorpy (or too thick n' chunky), thin it out to the consistency of melted ice cream or whatever looks about right. When you bush the paint on, try lightly dipping your brush in some thinner first. Then when you put your brush on the detail to be painted, it should just flow off the bristles all over the raised detail or small part. I find it makes the paint job look way smoother when it "flowed" off the bristles. With that said, use the right size brush for the job size. Few strokes as possible.
For bigger jobs, I spray with a rattle can, but for some stuff that may be impractical to hit with a rattle can could be brushed on in several thin layers.
Gloss colors are a sinch, metallics can be a pain, flat black will almost always look brushed on and rough in large amounts.
This is what works for me. Good luck!
Nathan