Hi, we used to have an old 68 candy apple red convertible mustang with a white top. The best thing that we ever found that is extremely easy to use is shaving cream. You just spray it directly onto the top and the dirt drips off. Just be careful of your paint job. You want to protect that. Do small areas at a time. You will be amazed at how well it works. It was the only thing that we found to really work.