Okay so just incase you have not figured out yet as to what type of primer to use. I have all ways used your basic garden stock rattle can of primer from the hardware store you can find it in gray, red oxide black and white. The only thing that you need to make sure of is that you have prepped the surface buy sanding using scotch brite sanding pad, wash it and let dry and spray, let the primer dry between coats sand if need be. This creates a good barrier, heck if you wanted to you can use automotive lacquer as top coat....I know you would not use that as a finish but I amtrying to demonsrate how durable the primer is. I have used this process for decades and have won several awards for paint jobs on my models. So good luck and spray away.