Anyone tried to rustproof they car?

Yeah, aside from the normal Sherwin Williams auto paint I used to paint the underside of my car, I used some "Bedliner/undercoat paint" from Napa for my frame rails (where I lift the car from) and it is junk. It's peeling off and I even cleaned the surface+primer painted it and scuffed it... It was like around 8 bucks a can, when I make it out in my shed again I'll let you guys know what brand it is.