I have primmered my whole car and have block sanded it. My question is that I primmered under the hood and trunk lid. It laid very nice. Do I have to sand the primer or can I paint right over it and clearcoat. I know it won't be as smooth as the outside of the car but will the paint stick without sanding??? Also, When I sanded the outside of the car the primer turned a lighter gray. If I don't sand the primer under the hood and trunk lid won't the darker primer give my paint a darker look than the rest of the car?? I had this problem before painting a car yellow. This car will be marina blue. Please help. I need to paint next week. Thanks, James

You have to sand it. All paint manufacturers have prep recomendations on their tech data sheets. They are all available on-line. Or get one from your jobber.

scuff with red 3m scotch-brite pad and your good to go!

scuff with red 3m scotch-brite pad and your good to go!

Not if it's surfacer, sand it.

I have primmered my whole car and have block sanded it. My question is that I primmered under the hood and trunk lid. It laid very nice. Do I have to sand the primer or can I paint right over it and clearcoat. I know it won't be as smooth as the outside of the car but will the paint stick without sanding??? Also, When I sanded the outside of the car the primer turned a lighter gray. If I don't sand the primer under the hood and trunk lid won't the darker primer give my paint a darker look than the rest of the car?? I had this problem before painting a car yellow. This car will be marina blue. Please help. I need to paint next week. Thanks, James

You should be using a sealer before the basecoat, this will help in your coverage problem.
Most (yes most) colors will not be affected by the primer or sealer color if you have sufficient film thickness in the basecoat to achieve hiding, ie: put on enough coats of paint.