Quick tips on stopping the rust on the cheap

Yes 70Sbird. Bottom of your clean car is perfect of a metal prep, or self etch primer, and go from there like you said..

Rust ecapsulators? That is simply trying to place a sealer over the rust where air does not get to that rust and keeps on rusting!!! yea right, what a solution. Blast off the rust to bare metal, best,... kill the rust, second best. POR 15,? yes I used some 25 years ago, Nothing tougher. BUT..... solution: clean the metal, self etching /epoxy primers, then 2k primer, sealer, top coat works much better, cheaper in long run too.