I agree with this..then when sanding the "ground coat" (ground coat is last coat of primer before the base) Go to a 500/600 paper to take off any nibbins or trash..I call it check sanding to see if there is anything to fix and then shoot the base..tmeyer said:The reason you want to use the coarsest grid possible is to speed the sanding steps. I am giving away all of me secrets to getting body work done fast. It does not hurt to use finer grid. It will just take longer with no end benefit.
I hope this helps.