I have used Deltron 2 stage urethane now on three cars painted in my garage.
The most recent was my 73 Ford Bronco body-off resotration. I used DTM 2000 a direct to metal primer. Sprayed one coat, dry sanded with 400 grit, filled the few little remaining dings and then sprayed another coat. I dry sanded this with 400 as well, cleaned every thing 5 times and then sprayed the Deltron DBU base coat with an HVLP gun. I then cleareed it with Transtar urethane. The result was OK. No matter what you do, you will get orange peel and overspray (at least I do!). I just finished wet sanding the clear with 1500 grit, and the result is spectacular. Even without polish, you can see the optical clarity at a good reflecting angle. A little polishing this weekend and she will be like glass.
I'll post pics on Sunday.
Mettallics are hard in a single stage. I suspect it is very difficult to color sand without disrupting the metal. Solid colors, however, are, apparently better in single stage.
All of these paints are solven based. The primer is reduced with acetone, the DBU uses an activator reducer that has 1001 nasty hydrocarbons, and the clear uses both reducer (I think it's hexane) and an Iso-cyante catalyst..you n eed a fresh air respirator to spray this stuff (I use my other compressor to feed the respirator.
I hate the prep work, but I find painting cars a very satisfying activity.
S