Metal shrinking is easy, you just have to learn how to do it. I took a body shop class at my local vo-tech, and was taught how. But it is a skill, and I suggest you practice on a junk fender first.
But the technique is, using a torch, heat the area you want shrinked, using a circular motion of the torch, keep it moving, but only a small area, 2 inches in diameter or so. Don't get the metal red hot, just heat for a few seconds. Then take a wet rag and cool the area by rubbing the hot area for a short time. You will find the metal tightened up when you push on it, the "oil-canning" will be gone. Then move on to a different area. It will take a lot of treatments to stop all the oil-canning.
