What I did with mine was I blasted them lightly. Just enough to get clean using very fine media. Silica sand is pretty aggressive on copper and solder. I used a blasting booth with what I think was aluminum oxide? it was very fine, almost like a powder. Then I Brushed them with a stainless steel or brass bristle wire brush, the brass brush gives the nicest finish when done. That smoothed out any roughness from the blasting. They look like new. Of you don't have access to a blaster try just the brushes. Stainless to clean and brass to polish. Good luck.
Henry