The trouble with things like brasso is they can leave stuff behind, whether it will here I have no idea at this point as I don't know the present/recent brasso formulations. I guess you could clean it properly afterwards in acetone or alcohol or something but that just seems like a lot of effort when you could use something better.
You see them more in flux pens but you can get abrasive brushes for using in electronics building ( https://www.sparkfun.com/products/retired/8967
). They look a bit like a felt tip pen but are not that (probably silicon carbide or something).
A quick search says dental gear has a variation on the theme, albeit without the flux, http://www.burdental.com/impregnate...icon-carbide-pen-head-polishing-brush-05sic05
, however that is going to be expensive as dental stuff tends to be.
By similar token if you wanted to get some ultra fine sandpaper that might also work, I don't like this option though if you are doing carts as the mask might not do so well -- you can sit there and drag a pen over each connector in turn, harder with a little bit of sandpaper.
A lot of connectors will be fairly soft metals to begin with which makes this a bit harder -- you can scrub steel with a brass brush quite happily and it will mostly just wear the brush away (something has to be harder to than something else to scratch it).
Plain contact cleaner (don't use the automotive stuff -- it is designed to cut through engine oil and proper oxides, not a bit of finger grease and oxide you can't even see) I guess could work but best would be far from it. On the other hand for springy pin female connectors it is about the only thing you have unless you want to play with flux and getting it on and off. Equally while I might repair cars and industrial equipment if a console landed on my bench and needed serious treatment I would probably tell the person to junk it instead, and with that in mind if basic contact cleaner does not sort it then call it junk. Sure if you have green death or black on one pin then scrape it off with a pick or something but if you are looking at something like http://s5.filetrip.net/p/46/299604-radar_logic_angled.JPG
then don't unless it is a rare and hard to come by arcade board or beta/unreleased device or something.