airbrushing gloss involves using more thinner, and more coats of paint. there has to be enough thinner in the paint to give it time to self level, but not so much that it drips off the model.
Proffessional finishes involve a lot of work. The color will be sprayed, and then wet sanded and then cleared; finely sanded again and buffed. That is pretty much the what you need to follow to get finishes that have the depth and shine of a true gloss.
The color coat sets the color, the clear adds the depth. Lots of clear will make the finish sparkle.
Pick up a copy of Scale Auto. Some of the finishes those guys do are basically astounding. The paint still looks wet.