Mistake understood and advice taken, guess it's back to the store for me! It is Testors gray primer, doesnt say sandable, and I got it because it was right under the models at Hobby Lobby, lol... Assumptions are the mother of all f'ups I suppose. It looks great but if I cant sand it... oops! Good thing I only did it on the interior and not the body.
I wish I could buy an airbrush but I just dropped a couple hundred bucks on everything and money is tight atm... Maybe in a couple months if business picks up I'll get a great airbrush set!
And thanks for the replies everybody!