Question About Sanding

Reminds me of an old song, says "Work your fingers to the bone and what do you get ???? boney fingers." I'm sorry bu it's true.
I guess if I were trying to do what you are atempting I would buy 2 kiddie pools from walmart. I'd use one to sink composite panels like doors, hoods, deck lids, in a paint remover chemical then a rust remover chemical then rinse and dry. Then the other to sink in primer/sealer. A liquid is the only thing that will go into every little nook and cranny. The finest blasting media will only get stuck in the crevasses. Most interesting blasting media I've seen is dry ice. Leaves no residue but still ... how to blast it into those hidden places ? Cut access holes for dental tools ?
I know I seem pesamistic but I'd rather you not develope corpal tunnel syndrome or even boney fingers.
I've got a couple small rust bubbles showing on 1 rocker panel (car was painted in 92) but so what. It's nature of the beast. Someday it'll need fixed and painted again. I hope the world turns so long for all of us.