I have been building bumpers for awhile now and I have been wanting to blast them before powder coat so the powder sticks better. I just have an outdoor blaster as of now but will be building a booth to do it in later on so that I can pick up the abrasive to reuse it. My real question is what is the best abrasive to use? I know that you can get the black fine coal slag, Aluminium oxide, or just regular sand all really cheap and in town. But I am looking for the best bang for my buck to give my bumpers a good surface to adhere to. I have heard good things about Steel bead shot, but am wondering what bead size to use.