I got the idea to use Mica Powders to Heat-Stain the header pipes on the Shelby Cobra. The first step was to paint them with gloss black spray paint. You don't need to coat the whole pipe, only the parts of it you want the powders to color. After painting, let them sit for about 45 minutes - 1 hour (you still want the paint to be "tacky", then add your first color powder (blue) to the top of the pipe, and use a small brush to remove the excess, then move on to your second color (purple), and when you use the brush, blend it with the previous color. Then just keep following on down the pipe. I get the colors I wanted, I just googled "Heat stained exhaust". Before doing anything to the model parts, I practiced on "chrome" plastic spoons I bought at Wal-Mart for a couple bucks.