A service reserved for the more discerning enthusiast, nerd, or car nut - actually that describes me - I do this weekly, but mainly because the spray from customer washes always hits my van. Or like today, immaculate van yesterday, this morning, bird poop on the bonnet.
Process
Goal: A really gentle wash to remove any dust and fine dirt, way less vigerous that the normal six monthly maintenance wash.
The goal is to remove contaminants back to the wax and then buff back to the original finish.
Using tap water will leave streaks and spots on the wax - deionised water removes the grit and dust etc, and allows me to buff to a perfect finish.