I started by covering the roof with Bare Metal Foil. I then tried an abrasive compound on it, going in one direction only with a coarse cloth...didn't work. I tried using steel wool, nope, not that either. I have thought about using some 12,000 grit sanding paper/film and dragging it in one direction over the foil but haven't got to it yet.

C1 powder...they are regular vendors at NNL East and always have some with them, usually selling out early in the day. Don't say it's too far, they come from England :) I have used it on many different cars and it works great. Just be sure to wear gloves and a mask because it will get in your skin and lungs if you are a klutz :)