I start with 800 on a hard block (Sometimes 600 like on this black 55 chevy I am doing now). And work every grit all the way to 2000 wet by hand. I will cut it open first and let it set a day or 2 in the sun or bake it in the booth. Then I will block it again on a hard block or the hardest block I can use for the surface. From there I use soft pads and semi rigid blocks. Even still, once you finish that 5000 stage and buff, you still might have to go back and correct a few missed scratches. It's just going to happen when you start with that course of a grit. I know some guys frown upon having to go back and sand after buffing, but I know how much clear I put on and how much I have to work with.
I think the more dust you introduce into your area, the worse pigtails you have. Have to think, running that da moves air. It's fine on small jobs, but when you have a full car there it can get messy...which is why I only use the DA with 2500 dry and then wet with 3000 and 5000. I keep my floor clean and sometimes damp and make sure all my blocks and sandpaper are clean religiously.
In a perfect world, I'd have a more dedicated clean room like an operating room for sanding and buffing........when I hit the lottery..........