Haven't been on for a while, but I have been reading my email notifications.
Part-Timer has it right...
I too can not understand why I don't have dozens of dealers wanting this. I have one consistent one and a few onesie-twosie jobs.
I am still using a 50/50 mix here in AZ. If I get much more spar, I have issues with it leveling out. We don't usually have much humidity. I do not do this all by hand, I have been using a simple drill and 3" discs. I too usually go as low as 400 up to 3000. I do keep some 320 and 220 on hand but rarely use it. I find that in the case of Dodge, and some GM vehicles if there is an area where the OE clear is in tact, it helps me to get that removed faster. I always strip the entire lens due to my past attempts to avoid that have left visible lines where the old UV clear stopped. The reason I use a drill instead of a DA is that, the lens is not as particular as paint. You really can not see the swirl marks once the Spar is on, provided you truly remove the more course ones entirely as you work your way up to the 3000 grit. It's only when I haven't removed all the 320 or maybe 400 that I ever see scratches, but I know once I complete the 800 grit step.
Also, this may help...
I always finish my power sanding, then take the disc by hand and go horizontally across the entire lens until I only see scratches in that direction. This acts like a guide coat, for me. If I still see swirls, then I didn't use the drill in that area enough, so I can go back and touch up. Also, it allows me to get every little edge, or corner that the drill may not reach in fear of hitting paint, or going through the tape. (ALWAYS KEEP THAT IN MIND) You don't want to pay to touch up paint.
Back to the spar.... My personal car has been done on 9/12/2011. I go to the gas station car washes and I am not the best at taking care of that stuff although, I like to try. They still look great, and I use them as a showpiece when I talk to new clients. Of course I have tons of pics of before and after.
http://www.facebook.com/pages/Light-Bright-Headlight-Restoration/209280115777811?sk=photos_stream
^ if you want to see some.
Anyway....Hope that helps a bit.