The claim to supply a powder which can plate copper busbars with silver "on the job". I do not have personal experience with this product, but I'd like to give you an additional hint on silver plating in general:
"Silver or nickel plating. This type of plating is being used increasingly where equipment is manufactured to american standards which require plated joints for high temperature operation. Nickelplating provides a harder surface than silver and may therefore be preferable. .... There is also some doubt as to the stability of these joints under prolonged high temperature cycling. Very high contact resistance can be developed some time after jointing. .."
cited from: Copper for Busbars, Copper Development AssoCiation (UK), 1996, p.40
I'd like to invite others to report their experience with the plating of contact surfaces in general and with cool-amp.
Suggestion: Check this Forum Areas for Chemical Engineers since you are requesting Chemical Process expertise from Electrical Engineers, which may be considered unethical. However, you could also surf web for the answer, e.g.
Plating metals through chemical rather than electrical means is called "electroless" deposition. Search the web for "electroless" and "silver" and see what turns up.