I just had my convertible done, and they used walnut shells to take that off. It took them about 10 minutes to do each rear wheel housing. Then they went and hit it with glass beads. Wow, it is now so nice (and done!)

When they went inside the rear quarters, they used the walnut shells again. It blew out that sound deadener. I wanted it out, as I did not trust that there was no rust lurking beneath it.

Walnut shells are wicked. They will leave some of the paint behind when taking the coating off.