Creative pyromaniacs, I have a safe solution for your fiery needs. To avoid actual flammable materials, take a look at Flame Painter from Escape Motions. A “unique paint application that lets you easily create original artworks, design or light effects with procedural brushes,” you can change up the color, brush/flame size, saturation, opacity, speed, focus, and more. Lotsa options to create whatever kind of smokey flames spark your interest.
The image above as well as the ones below are ones that I did quickly while messing around and trying out the tool. It’s super easy and quite fun. Definitely worth playing around with!