Never heard of the WD-40 thing.

You may be better off parking the car over some plywood sheets or carpet vs over bare concrete? I had a rental storage unit I put a car in and the floor deep into the space had constant damp spots on it. Concrete will absorb water and sweat it out wherever it wants to. I bought a bunch of thin plywood and spread it out to help block the moisture from coming up.

TTI should just make their headers out of stainless steel as an option for those that want it. Price would go up, but it may be better than going in circles with coatings. I knew a powdercoat guy here years ago who would do header coatings too until the material price took off and it became way more than what reasonable people would pay for it. Like as in the coating application was about the same as buying new headers.

Jet Hot is expensive from the one item they did for me. Look into Cerakote and see what they have and if there are any applicators in your area.

BTW I know someone who had their Hooker headers ceramic coated locally years ago and they got some chips and oil stains on them that would not come out so they painted VHT header paint over the top and they have looked good since then, Not as shiny as the ceramic coating though.