You could actually take an emery board, not the metal kind please, use the paper/cardboard kind that you wife has a dozen of, and pull it in and out of each outlet hole a few times. It will scratch the surface, giving you better contact.
Note: it would be best to flip your fuse off before doing this, if you leave it on, and you get a shock (you shouldn't get one though) it is on you.
By all means be as careful as you can when working with alternating current. At 120VAC the maximum let-go threshold is ~ 15mA for a male. 500ma will get to fibrillation - no place to be. I make sure that I'm well insulated every time I work with AC. Comes from working with 1 MEV for a living and my electrician Dad as my mentor.
Cleaning with an emery board will certainly get rid of oxidation, but you MUST use a contact enhancer or preservative if you do so. When we talk about electrical contact, the better micro-finish we can get on the contacts is extremely important. When I was an implant technician in the semiconductor industry I got to see many electrical arcs. How about an arc over two feet long drawn from a surface that had a tiny burr from a screwdriver. Electricity is going to find the shortest path between two surfaces while generating a connection. Electron microscope images on electrical connections are very telling about surface effects of conducting materials with mill finish and polished surfaces. The mill finish (like you see on most electrical connectors) is relatively smooth to the eye and mountain ranges at microscopic levels. There is a tiny thunderstorm going on between the "mating" surfaces that is not a small source of RFI. When we clean electrical connectors, using the finest abrasive available is a very good idea. A popsicle stick trimmed to the width of a plug blade with 600 grit sand paper (or finer if you can source it) is a really great little tuner upper for receptacles. Then finish the job with the contact enhancer of your choice. Dip the popsicle stick in the goo and run it in and out gf the blade slot a half a dozen times.
Contact enhancers: DeOxit is fine, just use as little as possible. I use Jena Labs contact enhancer. One bottle is literally a lifetime purchase for most of us. Another great contact cleaner/enhancer is Pacer Rail Zip for model train tracks. Formulated specifically for removing oxides from brass it works really well for all types of contacts: [url]http://www.supergluecorp.com/?q=zap/zap-rail-zip/url]
Gotta keep this contacts clean!