There is a product that I recall using in the boat yard I once worked at. Anyway, this stuff removed rust instantly. I used it on propellers. Which if one tried to clean the rust any other way......they would be there for ever. Anyway, a boat store or perhaps Loews or Home Depot would carry the product. Though I am not sure if it can be used for this delicate work. Perhaps a small amount with a small regular hobby brush will do the trick.
Anyway, I cannot recall the name, but it is very strong and very toxic as I recall. Not the sort of stuff I would use around children.
Pete
Think it's called Naval Jelly but you must rinse it off when done.
Also , Ihave a number of lionel tinplate track in very good condition if interested.