Am I ready for the last coat of primer

I normally start block sanding with 220 then move to 320 (with guide coat of course). If the primer has more texture (orange peel) than normal, I might start out with 180 (all PSA - sticky back- in Dura Block sanders. After finishing with the 320, you have a decision to make. If the primer looks good (all the guide coat is gone and things look smooth), then block it with dry 400 and then wet 400 and wet 600. If you need to tweak a few places, then stop after the 320, fix the bad places, spray some more primer, and then start with the 320 again. I know it sounds like a lot of sanding, but good surface preparation is CRITICAL.