I live in upstate NY where salt is king. My answer, and it works, is WD-40. Spray the heck out of everything. Let it drip dry on a gravel or dirt area. Will take a few days to stop dripping. Puts one heck of a film of rust preventer in all the tight places. Cheap too. Pop the plugs on the doors and the screws on the step plates on the door sill. Squirt it in real good. Another favorite place is under the rear wheel wells. The sections on the bed that are on the corners of the wheel well section of the bed are great dirt catchers. Make sure you wash these spots regularly as well as the lip of the rear wells. That's where the bed will start to rot. Same deal with the tailgate. get the bottom seam wet with WD. Do this before winter and after things dry out in the spring.