I am a driveway body man so look for more input before you go with my method. That said, at the blocking stage I use 320 to start with which will knocked down most of the the peaks. Then spray more primer and sand with 320 until the low spots are gone. Then moved to 400 then up to 600. I would use the 16" on large panels and 11" for smaller panels. As far as brand, I don't know, but I would go with a wet/dry paper. Wet sanding cleans the paper and last longer.
Good luck.
