I don't think I've ever "cleaned" any connector in all my years in RCing. Deans, Race Prep, Power Poles, EC5, XT60, 3.5mm/4mm bullets, low profile battery connectors "bird cage"/pronged ...etc. etc. etc. They all are basically self cleaning unless you are submerging them in honey or something. Even had some cheap new EC5 connectors starting to form a weird greenish tarnish on them. After a few connects, and disconnects, the tarnish got swiped away.
Speaking of Tarnish (band I was in):
RustyMe
RustyYou
RustyUs