PPG's base coat does not require 1000 grit for top coat,I spray it everyday all day long & have since it came out in the mid to late 80'S! 280-320 grit is as far as I go on a 6" Da. I never get sand scratches.

I was one of the First in the states to try DBU out & I know all its quirks. I can pound that stuff as hard as all get out & never have a problem with it.
What alot of people dont know is you can spray lacquer clear over DBU after an hour dry time , that was the required way of doing it when it first came out.

DBC is a good product , but it has a little bit of a lift cycle, if you dont know all its little neuances. Plus it doesnt have the catylised reducer like DBU. DBC will move on you when you clear it , if you pour the clear to it . But it does have a catylist that you can add to it ,to make it more like DBU and more forgiving. but then the cost factor goes up.

DCC is a good product , BUT it requires you to add mixed clear to the mixed color for better color hold out ( PPG's recomendations ).
DCC also has a delayed flow action that alot of guys cant get the hang of , it looks peelly & they will always do a double coat , there fore run city.

PPG's DP & DPLF is a sealer not a primer that requires sanding.It is more of a sealer, spray it just before you put paint over the top of it . I dont like it since they went to the Lead free.
It also comes in several color & they can be mixed together for different color variations, so it doesnt require as much color for coverage.

SprayTech