Everyone has different ways of doing things, ive just said how I repair and paint cars everyday for a living.

Wet flatting primer with 600 or 800 wet and dry has died a death in modern bodyshops, the only time a use a little water is flatting the top coat down. Even machine polishing is done dry now days.

Remember using a DA creates a lot less sctatching hence a courser grade of sandpaper can be used.