Not sure what you want to clean...raw copper buss bar, tinned crimp on fittings or the surfaces under bolts? You can use wire brushes
...both flat and round, or use chemicals or acid or green scrubby pads. Lots of choices that work
. We use Boeshield T9 on electronics and Tef-Gel on the heavy wires. A hydraulic crimper..USA not China
..and heavy lugs . We tried another spray but Boeshield is the best stuff. I think it came out of the aircraft industry.
Tef-Gel is expensive but worth the cost. Simply better than any other product we have tried. Two different, slightly expensive products for different applications but you will find they work
Happy trails to you.
Mark and the manatees