rust proofing door pinch seams advice. (late model)

Door bottoms aint the worst of it. Open the trunk then turn /contort to look at its turn down lower pinch from the opposite direction. This is the very worst spot on every a-body I've owned.
I use a very fluid, milk like, water based product, first was called Neutra-Rust, later used Rust Ender.
After a good cleaning with compressed air, Generous application from a pump spray bottle then pushed it with a whisper of compressed air.