I took a class from Ron Covell, I was amazed that he took a sheet of aluminum and a sand bag and started beating on it. It had a bunch of lumps, he then worked it on his english wheel to smooth it out to get the compound curve. I had always tried to gradually work to the shape I needed. an old soft leather purse filled with sand works almost as good as an expensive beating bag filled with buckshot. Check out Cboys build threads here on this site, He has a lot of good how he did his cars I took a panel fab class at UVU. Check out one of the students build. google "chris davenport 40 willys "