Are you wanting to keep it looking like it is? Patina?
Anything you add will make it shiny. Sweet Patina is owned by a friend of mine, I haven't ever used it as I just wax mine.
I do have a 68 that is "rusty" patina, I am probably going to go over it with Comet and then CLR to see what happens and then probably wax it.

I guess it depends on what you want it to look like.