Originally Posted by GullyFoylesbike

Some more research has turned up an interesting route - musical instruments get dents repaired using a set of ball bearings and a large magnet - bearing goes inside and the magnet is used to drag it along / pop dents out. I live about a half mile from a local shop that lists just such repairs on their site, so I'm gonna pop over there this weekend maybe and see if I can get any thoughts or info out of them