Not sure what CC edge connectors look like but to clean male and female pins etc, i buff the male with steel wool or fine grade sand paper.. sometimes ill flow some solder over them also to make good strong contact.
My trick to clean the female is to shove bi carb of soda into them and then put in a bowl... pour on more bi carb. Then pour vinegar over the top... will fizz like buggery... allow to stop fizzing and pour some more... leave for an hour and rinse off... gets rid of most if not all the black grime!
sounds like an 'old wives tale' to me 
Old wives know some stuff ya know...
