A good pressure washer is handy for that too. The air gun works as well but not one of those safety ones with the pressure limiter, wear gogs though, flyin bits of paint in the eye suck. Try a spot with a heat gun and wooden or plexiglass scraper, you never know.
Sanding will work but when you are working on the edge of one of those peely spots you end up sanding too much of the OG paint as well. By the time you are ready to buff the white is gone, especially places like under the windows where it's already thin from time.
