I picked up a gheenoe that has a big rust stain on the front bench. I used star-brite on it and lightened it a tad and got rid of the rust everywhere else. I'm wondering what would get rid of it or would I have to paint over it. I've heard of a few other things like bar keepers friend and toilet bowl cleaner. But I've been using star-brite for several years and it has worked on all my rust stains except this one. I'm figuring those others won't do any better. What should I do?