[suicideneil]

I use lead free solder with a rosin core, not sure on the exact composition but I find it works extremely well for me. Silver-bearing solder is meant to be the mutts-nuts but it was kinda pricey so I went with the cheaper option at the time.

I don't use extra flux anymore, haven't found any need to.

A little rubbing alcohol might work yeah to lift off the carbon, or maybe some comm drops designed for cleaning up brushed motor commutators, though some brass polish might work well afterwards to really polish the connectors. If they are heavily sooted then it might be worth braking out the wire brush attachment for your dremel, then polishing them.