start with 1200 grit on a stiff 3M rubber sanding pad or a paint mixing stick.. get a large bucket and fill it with water, throw in a sponge. stay about 1 to 2 inches from all the edges. blow throughs suck, keep the car and paper wet at all times..
Call your local Ardex dealer up and get their 1500 buffing compound.. after your done buffing get some 2500 polishing paste from Ardex and polish away ! Your car will look like glass ! the buffing and polishing work better with an electric buffer, but come out just as good by hand.. it just takes longer.