I don't like using primers on touch up jobs and here is why. You are usually working with a thin layer of paint already. When you touch up with a brush it is uneven at best. You can sand it down but still it will have to be recessed to work well. If it is not then when you put the top coat on then sand the primer will come through every time. Nothing worse then seeing your primer through the touch up paint. That is the international sign for "Do it again". RustOleum it good paint and does not need a primer. I have done several bikes with it and it always worked out well. It has a real long drying time if you want to work on it. I have found that letting it dry for a week between coats is best. Bad part about rustoleum is the limited colors. You will most likely wind up with nail polish for the metallic grey. All metalic paints are almost impossible to do a good touch up on. The metalflake embedded in the paint takes a direction when it is sprayed onto a frame. No matter how you try, you cannot match that flake pattern exactly. You will alway see where you have touched up a metalflake paint. Good luck.