Ive had Line-X in mine since 2010. Held up great. Just whatever you use try to get the bed bolts up and out of the floor along with any tie down hooks in the bed and reinstall them when you're done. Makes life much easier later on if you ever have to pull the bed for a fuel pump or whatever.
I got mine loose and the Line-X place pulled them out before spraying and reinstalled after. I also had them do over the top bedrails, down the bottom inside lip of the tailgate, and the back lower part of the bed thats behind the tailgate bottom. Been happy with it. Theres a lifetime warranty with it so if you tear it up somehow just bring it back and they'll fix. Its expensive though....I think it was about $500ish for mine back then.
'03 XLT/FX4 L1 4x4 4.0 Arizona Beige Automatic (my weekend ride). '16 Ford Escape Titanium ecoboost (wifes ride) '16 Ford Escape S (my work ride)