Learn something new everyday (Preventing Rust)

[Wizard52]

GU is now 18yrs old and goes to Fraser a couple of times every year so rust was always going to be a problem sooner or later. Had windscreen replaced many years ago and a dodgy job did not seal it properly. Got a couple of chips on new screen recently and before I could fix them, a crack started when hit by another rock. So replace this windscreen and found considerable rust in channel above windscreen.
While getting repair done, found more rust in bottom of mudguard as in photo although I have always cleaned the sand out but obviously not well enough. Panelbeater showed how to make sure it is clean by undoing two bolts at bottom of picture and gently pulling bottom out enough to get hose or compressed air in from end near the door to get all sand out. Real easy with 10mm socket. Let air dry and spray your choice of oil or Inox etc to cover up inside. Will do this every time back from the Island, probably 3 time this year.
Not sure if same on Gq.
Marks in photo are stone chips which have not rusted

[PeeBee]

I would recommend before application of the anti rust system that you thoroughly wash the area with a rust converter product - plenty on the market - Bunnings have a suitable one, as this will arrest the chemical conversion process by converting the rust patch into a benign element - then apply the preventative coating, wax, oil, donkey drippings, whatever over that, I found minor areas of surface rust in the donor body on the GQ and bought a couple of bottles of the Bunnings converter, loaded up the plastic syringe and doused very crevice including the roof , windscreen and doors with it, saturated the car and floorpan. I am relaxed about rust prevention with this approach.