rust encapsulator? myth, fantasy, reality?

[Pinchecharlie]

iam about to start painting my cab. I have a realitivly straight cab but its has bad paint job and worse it has the tail tale signs of rust beneath the surfice and worse in cracks between panel attachment areas. well...i had hoped to just scuff the old and seal and start over with paint. but... cant paint over rust. i really dont want to blast it because i know ill find a bunch of problems and i only want a reasonable job not a show finish. i know its a long shot but do any of you body shop guys have a magic product that i can spray over the rust to keep it from bleeding through? If the paint held up for a decade id be ok with that and then i could just say it was a patina in the makes. disclaimer: i know this is not the right way but iam starting to have anxiety about the can o worms in a paint job $$$$$$$$$$$$$$. long shot i know but just wanted to ask. thanks charlie