I did have a US friend who lived in North of Boston, on the coast. He had an old school Aston V8 which was Aluminium and could suffer in the same way.
He was a little OCD. Well a lot OCD truth be known. But its not a slur is it, it's a compliment.
He had a concrete driveway, he got a cutter and put a grove in it. He then glued in a super soaker hose which fired upwards onto the underside of the car. The hose ran to a switch he could lean out of the car and press with his foot.
He would drive up, hit the switch and turn on the spray, drive over and then walk back and switch it off. You could do the same with a low power jet wash, strong hose and thin drill.
