How do you repair a rust stained running board?

How do you repair a rust stained running board?
I think you can get it at Wal-mart, it's called Barkeeper's Friend. Pretty sure it's cheap. It comes in a can that's gold and blue. It is powder, and if you use one of the rough green cleaning sponges, or a brillo pad, and add water, it will remove rust from metal. I would suggest the green cleaning sponge over a brillo pad, just to be careful not to scratch the metal.