I'm assuming its rolled and pulled? If its the type of pull I'm thinking of where the fender lip is virtually the shape of the upper part of the wheel that is tucked under it; it may be difficult to get that semi circular crease out. I have not attempted this myself, but I'd imagine with a lot of heat from a heat gun (or torch if you dare), one could probably persuade the fender back in a bit.
In order to do this one would probably have to have a flat surface, like a 6x2 board (or some other non-metal surface with a large surface area) with a soft cloth wrapped around it to prevent marring, a heat gun, mallet of some kind, and some time.
If I had to do this myself, I would start by heating the inside of the fender, the lip of the fender and the outside of the fender (similar to the way they were heated for rolling/pulling) . The main focus of the heat should be up near the crease talked about earlier, since this is the point at which the fender changes direction at and will be the point at which there is the most flex in the paint. I would then center the large surfaced flat board wrapped in the cloth over the crease starting at the top center of the fender and hit the cloth wrapped board with the mallet a bit. *One would have to make sure the edges of the board are not making impressions in the fender too (one way to do this would be to make sure the board is really wide or on a convex surface). I would work around the fender from the top outwards on either side (like rolling); with constant reheating of course (like rolling).
Last edited by cleantune; 04-29-2012 at 12:10 PM.