the problem with sanding with an air tool or blasting is it will ruin any body work that has been done.....you need to experiment with a small area
I had a job go bad about 25 years ago, (old hardner, opened can, lesson learned)...... fortunately, I used a quality epoxy primer (Glasurit). I used stripper to remove the paint, and it did not attack the epoxy........ stripped it, cleaned it up, resanded, and painted......... I ate it, and it took me a week, but could have been worse.........it was a 64 vette