All,
I have seen folks ask this but not sure I ever remember hearing my solution for it...
I found that a strait razor, like what you would use to clean paint off of glass will cut old undercoating right off of the under side of body parts. Just lay it down just like you would if you were attempting to scrap the paint off. I was somehow able to get between the paint and the undercoating and pretty much cleaned it right off. I tried to use my wire wheel and that took too long the razor blade did just fine for me. In my case, I mounted it in a holder and went to chipping it away. Be careful not to cut yourself for sure.
