Hi Dom
If it's rusty under the arches then forget waxoil... it's simply pants... use Bilt Hamber stuff like Deox Gel and then Electrolox primer.
With regard to the tailgate and arches:
(Im currently in the process of touching the arches up in order to refit the arch kit and I'm also picking up a standard tailgate in a week or so)



Sorry for the crap photos - it was getting dark out and could only be bothered taking pics with my instant