When I was just starting out painting cars(mid sixties) we used to warm the synthetic enamel on a hot plate to thin it and shoot it without thinner. it gave an incredible gloss, but was risky. The warmer you make the metal and paint the better, to a point. you don't want the paint drying to fast, as that causes a lot of other problems. If you take some time to experiment, you'll eventually get some great results. good luck.