Anyone tried to rustproof they car?

I've seen holes around the windshield post/frame for sure, thought I'd try to shoot some UP and down that area too. There is no way to prep these areas, but if I can get some air blowing inside that may clean out any large globs that have accumulated. dont ask me where the junk can go, cause I really dont know!The Eastwood product someone used looks pretty good, although I have used Rustoleum RUSTY METAL PRIMER for years. IT CANT HURT!

THANKS GUYS!

Picture of the day! This is the trunk floor in a 72 Challenger I bought to re-do. I gave up. Tallahassee Fl is the humidity capital not only the state capital of FL. If you look close you can see the sending unit- that was all that was left of that gas tank!