Nuther question....what grit can I use to block out the body. 150 (dry) seems too agressive but 400 (wet) takes toooooooo damn long ( I luv body work). Can I use like a 220 dry or ??
If you are really trying to "block" something straight, 400# is to fine for the first pass. Remember to use a guide coat. Blocking means cutting the high spots down and exposing low areas. 150# seems agressive, but you need to cut the high spots without just rolling over them like you will with 400#. I use anywhere from 100# to 180# for the first block on HIGH BUILD primer. "Back in the day" with non catalyzed primer and lacquer paint, this process would take at least 6 weeks to several months for custom work. On the flat areas on the quarter panels cris-cros "X" sand with the 150# just enough to see you are flat, then switch to 220# with the same technique just to cut the 150# scratch down. At this point stay away from the body lines. Very carefully do the body line areas with the 220#. Very low spots will need filler (Glazing). If you see a lot of bare metal or the primer is getting real thin, it's going to need another couple coats, probably reduced with just a little thinner to smoothe out better, at least in the spots where you really had to block and took a lot of material off. If it seems straight before you put the last coat of primer on, then you can final wet sand with 360 to 400# (single stage urethane will fill about 360# or finer wet sanding). If you have some small bare metal areas after this (thumbnail size or smaller) the sealer will be OK to cover these. The black sealer is going to show how well you did, so set up the lighting for the sealer/paint so you can see how straight the body is as you spray.
After all this work, you will find you have NO fingerprints. Time to see if a life of crime is for you.