Looking good Charlie. Tamiya and testors lacquers are safe for bare plastic. I have many builds no primer. You could use Tamiya fine or medium compound and rub it out instead of sandpaper..
I watched the guy on CNN who investigated this and he said best I could remember the price per car to fix it was 91 cents. My wife owns an 08 g6 and GM service is awful. She does not want a Gm nothing...