prime the whole car 3 heavy coats. that will gaurentee your dont have any assholes when you paint. get a flat block and some 3m guide coat. rub the guide coat over the whole car and wetsand with 600. untill you dont see any of the black from the guide coat. make sure to keep your block flat that will also show any low spots you can address with filler or not worry about it depending how far you want to go.