use 400 Grid Wet Sand paper. if you want to save time hit it with 80 Grid Dry Sand Paper and then go over it at the end with 400 grid and make sure its all smooth and no deep scratches, and then go get a compressor and a gun any kind of gun cause its just primer not paint, and set it on 80 psi and spray it on wet and I think its Layer over lapping layer. and at the end make sure to clean your gun and dont let the primer dry inside of it or its gona be a bitch to clean.. Well Hope this help.