Hey welcome to my geek blog! Time to jump right in...
I'm building a Stompa for my Warhammer 40k ork army. As you might well know, superheavy vehicles and titans are fire magnets. With armor 13 the Stompa is tough but not invulnerable, so its gonna take some damage during a game. I figured what better way to represent this than to have a few damage markers:
These are magnatized from the inside, so there are no visible magnets on the outside of model.
To make these, I glued a magnet to a small button, then glued Woodland scenics clump foliage to the button, building up and off of it in a smoke pattern. When the glue is dry, prime in black and paint in shades of yellow oranges and reds, with greys and browns for the smoke. (remember: white is the hottest, followed by yellows, oranges, and reds.)