Redundant but,…
Heat Gun and i used a little bit of Zep cleaner (probably comparable to acetone or naptha, but less harmful.
We just sold a couple semis and work and all the stickers had to be removed, (fun project)
Another suggestion though, at CarQuest, we have a lisle tool that is pretty much a screwdriver that holds a razor blade, but it comes with a plastic scraper (could probably find something similiar anywhere). Very handy, have used it many times to remove decals off the race car.