It depends what I'm starting with, and what final result I want. Clear with wave needs a coarser grit than 2000 or you're wasting your time. Clear with minor orange peel and trash, 2000 is fine. Using a block initially does help highlight dust nibs, and will flatten the clear slightly more than a da. On a normal nice collision type job, where I want the texture to match, I just hit it with 1500 on a da dry to highlight dust nibs, block those out with a small Tolecut block, 3000,8000, buff. Really no need to block after the initial grit, because you're just refining scratches.