Is wet sanding primer needed before colour coat? (picture)
 

http://i.imgur.com/TPItNbo.jpg


I removed rust from underneath the trunk weatherstrip, and painter primer over the area. I have red paint to put on top, and then I'll install a new weatherstrip.

I saw wet sanding the primer with 600 grit done in guides online, but I don't know if it's to help the pain stick, or if it's just for a perfectly-smooth end result. The area that I've painted is going to be covered with the weather strip.

What should I do?

You dont have to wet sand it, dry sanding is fine. But depending how thick the primer is, it can be block sanded for an even smoother finish. Also to help with paint adhesion as well.

Some of the areas that I've painted primer on are seemingly too thin for me to effectively sand - like 0.5" wide, before the tape. Is it OK to not sand those areas, and just colour paint over them as is?

I gently sanded the primer with 600 grit, and while doing so there is one spot that sanded through to the metal - just a bit. So, I put new primer on top of that one area, and let it dry for about 2 hours, and then I put the colour coat on top of everything.

The colour coat dried very quickly, and now I'm wondering: Was waiting 2 hours for the patch with new primer enough time - and should I sand that area down again and reapply primer, wait a couple of days for it to fully dry and harden, and then apply topcoat colour?

Coz the newer primer still had some solvent or whatever wetness in it, and I don't know if it will evapourate with the colour coat on top of it now.