Auto body repair & detailing: rust/discoloration, paint nothing, nothing fancy

Question
Just bought a 1990 Pathfinder and would like to know of any way to fix discoloration from what looks like rust running down the paint. Nothing fancy maybe just to get it somewhat black again. I know there are a lot of questions similar to this but i would very much appreciate any information you would be able to offer.

Answer
Try rubbing compound, then follow up with cleaner wax. This will be a temporary fix, though. The rust is the problem, not the staining. Being a 1990 Nissan, I highly suspect that the panels in question are starting to rust through from the back side, and what you are seeing is a product of that. The bleding just doesn't appear out of thin air, it's
coming from somewhere. Bill