Thanks for the encouragement. I've finally discovered the best way to strip this paint--I scuff the white down with a Scotchbrite pad on my air-sander to thin the paint, then apply "graffiti remover" aerosol, then scrape off white with a plastic scraper, then use acetone to get off the final white bits and finally polish the grey. The graffiti remover is really acetone suspended in some kind of jell that can be sprayed from a can. It sticks to the paint long enough to loosen it but so far hasn't done any damage to the 63 year old VW paint!