Just went through the same thing removing gaskets from my toaster project. I found a razor and Goo Gone were all I needed. Coat the gasket remnants with Goo Gone, let soak for 5 minutes, scrape at 45 degrees with the razor. Repeat if necessary. The bad ones took three passes.
Nice project, keep it coming! My wife's cousin is in Atlanta - I might need to head down that way when my toaster is done!