I did this one on explosions a few moons ago;
http://www.joedios.com/forums/showthread.php?t=713
As for flames, Paint Shop Pro has a tool called "Tubes" that paints on weird little effects...one of them happen to be flames. If you don't have it, you can try JoeCustoms, they have a link to a JoeWiki that has a "Flames" file for Photoshop that you can cut and paste onto a pic.
hope that helps!!