I have been using some good old Brasso metal polish, takes a good bit of work with the wadding though.
Polished a few up recently, the d25c ti which does not show too well in this pic
Little bit of cu as well
I have also polished up the pocket rocket from Daniel, breathed on by gunga(219b and h17f). To remove some fine scratches from use(how the heck do they get there!?!)
Its not something i do regular, just every now and then(few months gap then go on a polishing spree ). I like the patina on copper, also like starting it again