Deoxit (the red original kind) is the best stuff, it's great for switches and contacts and all sorts of things, some of which can't be cleaned by hand. In your case though it should be a simple matter to use some metal polish or very fine sandpaper, and wherever the light makes a mechanical electrical contact.
A list off the top of my head are the lamp center contact, the lamp outer spring (around the bottom where it contacts the light body), the rim inside the flashlight body that the outer spring contacts, the tailcap spring, the inner tailcap contact and the base of the flashlight battery tube which usually makes contact with part of the tailcap switch.
I'd clean the outer spring and center bulb contact, the battery ends if they look even a bit duller than when new, and the tailcap spring. It should take just one or two passes with the sandpaper to brighten up the metal, you aren't trying to remove it, just cut through the oxide buildup. Deoxit does this chemically, but abrasives work just as well, not nearly as convenient though (it's great for tailcaps and other non-easy to clean areas), and deoxit has the benefit of keeping stuff working so you don't need to hit it with abrasive paper as often.
There are no contact points on the Commander. The buld is designed to make contact with the battery only; both positive and negative contact points are on top on the battery.
I think the bulb has had a long service life....time for a fresh one.
I've never owned one personally so I'll take your word for it, but it seems odd what with the battery having pos and negative contacts on opposite ends. The pictures I've seen show a pretty run of the mill surefire build, with the same contact areas as any 6p/g/etc light.
