Originally Posted by BamaCraft
A DA in the automotive world is a Disc Action sander. I took that as wanting to use with ultra fine wet sanding. Ive seen that before and doesnt turn out so well. We call what you refer to as DA posher as an orbital buffer. I use one frequently too. Great to use with liquid wax but for compounding etc.. A variable speed buffer is the only way to go.
DA is dual action not disc! But you have the description correctly. Using the word Orbital or random or dual action means that instead of having central axle around which the pad spins (like say a drill or angle grinder) There is actually a central axis with an offset connection to the pad, the offset rotates as does the central with the concept being that if you sit in one place the pad never "turns" in one spot.
DA's are great because they don't burn paint. BUT like you nailed - they don't remove the layers. So when you want to throw a nice buff job on the hood of a Mercedes benz that DA won't screw up the paint - but when you want to remove oxidation you won't do it with dual action.