I'm sure many of you all have figured out how to do fire, but I haven't really seen a lot of fires in paintings, around here, and I quickly looked through the tips and tricks section for a tutorial on fire, but I didn't see one (at least the text string "fire" never showed up) So I thought I might provide one really fast.
I find it's best to paint a fire on a dark surface. More fun with light that way. I've got a flood of images coming here, most of them full screenshots for tool settings so you can sort of see what I'm doing.
Here I'm just building up a basic image of fire with oils on a separate layer. Start with white at the center, work your way out to a light orange, or whatever color you want your fire. I suppose a fire could be really interesting in purple or something.
Early to bed early to rise makes a man stupid and blind in the eyes - Orson Scott Card