anyone know how to treat underbody rust? I have a 2002 grand am gt from Michigan it has low miles but quite a bit of underbody rust. I tried a spray on rust thing it was supposed to turn the rust black so its not so noticeable and prevent rust and it didnt even turn black.... I'm getting ready to sell the car so I really just don't want it to be noticeable.. Please no stupid "Grand Am" jokes and please no trollling by saying black spray paint. what do you guys recommend for less then $50