This is my 2007 Saturn Aura. When I got it the trunk/bumper had more scratches than I could count so I just decided to paint it. When i did it I was a newbie and didnt sand it at all before painting. Now ive sanding it with 600 grit and now the trunk is pretty smooth minus a few spots. Now I'm wondering do I need to sand with a coarser grit now? Also, if i dont need to sand do i need to shoot primer before i do my base and clear coat? Ive been told after basecoat to sand it again after waiting a day then clear coat it? thanks.http://s1373.photobucket.com/user/Robert_McClese/library/?sort=3&page=1

600 is good to paint over. Definetly dont wait a day and sand inbetween base and clear. Shoot last coat of base and then wait 30 mins and spray clear right away def dont sand. u can use a tack cloth in between coats if u want, and if its metalic dont use tac cloth after last coat.

First thing is to make sure you've removed all the paint you put on without sanding. The "few spots" you mention can't be there - it needs to be 100%. Near enough is not good enough in this game. If you haven't broken through the clear (or topcoat) then you can go ahead and spray your base, then clear but, as mentioned above, never sand your base. If you've broken through then you'll need to prime those areas.

So just keep sanding with the 600 grit until its totally smooth? How do i tell if Ive broken through and need to prime?

You'll see the colour change if you go through the clear. I prefer to use P800, it's a bit slower but still gives enough adhesion.