this weekend my buddy and i are going to spray my bug this weekend with a couple coats of primer. But i want to get used to spraying it and dont want to spray an expensive primer. but i have primer that i bought along with my paint but i dont want to waste it. is there a problem with primer compatibilities or is it just bc's and primer? so basically lol can i just go to the local automotive paint store and pick up a gallon of primer to block sand and get the body a little more smooth?