Steamy- I'm in the middle of wet-sanding my 1989 Porsche, also with single stage, original glasurit paint. I'm using 1500, 2000, then 3000 grit paper. If you are taking it to a 4000 grit finish, most of your work is already done. If you are terribly concerned about burning your paint, I can tell you that the combination of the Porter Cable DA, Lake Country Tangerine pads and Megs 105 takes the sand marks right out, no problem, leaving, in my case, an extremely refined, mirror-like finish. I then switched to a white LC pad with 105 to refine it a bit more and take care of more delicate areas. At this point, I'm curious to see if polishing with Meg's 205 will make the paint look that much better- I'm truly stunned with my results!
I use the 4 inch pads for tight area's and a 4inch base with a 5.5inch pad for concave angles.
With the Porter Cable 7424 unit, you can (and should- finishes better) put more pressure on the paint, so once again, no issues with burning the paint. Granted, I would always tape delicate areas until you switch to the white pad with less pressure- big difference in cut between the Tangerine and White pads.
I have to agree with PAR though- I wish I had a trigger.