Rust Proofing?

[Litemup]

Quick question for you guys about rust proofing. I have a truck that has solid metal on it in the usual area's, rockers, corners, bottoms of the doors. The truck was a Cali truck and now its here in WA and its being exposed to our good ol' washington weather. I want to try and prevent any rust from happening in the usual area's. There are some holes I need to have filled at the body shop, until then I have some tape covering up the holes but I'm sure moisture is getting in. I know they make sprays but I'm wondering what you guys have done, like how to get rust proofing inside hard places.

Thanks in advance!