When I had my Allergo Bus painted in Red Bay, Al, the workers just used razor blade scraping tools, the common ones sold everywhere. They had all the decals off in and hour or so with no damage to the paint. I'm thinking that this wasn't their first job, however. They claimed that the Snap On wheels were way too expensive and much slower.
Today was new decal installation day. Went to an awesome graphics/sign shop in the area. They did outstanding work, and the only issue was that Tiffin didn't include 3 decals on the shipment. I emailed their parts department and they agreed to ship them right away. Here are some before and after pics... you can still see a few missing on the final product, but you get the gist.