One episode of Rides on TLC featured Mike Lavalle who makes the most realistic flames you have ever seen. He was painting a 34 ford I believe and it took him about 20 layers of color and 10 or so colors, red, yellow, white , and some candies. It was something else to watch. If you get a chance watch that show. Like any airbrushing you will have to find your way and creat your own 'style'. Practice on everything. Even the garage wall!
Check this out!