Hi . Have u tried a vacuum pump to pull it ( the type u use to lift glass ) I work in a body shop and have seen our lads use them if the dents not creased-
Aren't they usually used on big dents where the panels pushed in, say like a big dent on a door? Also I think there used before using a slide hammer and welded pins. Dont think they work on minor dents that can be pushed out but don't quote me on it!