On the n810 you could hold volume down and tap for middle click or hold volume up and tap for right click. It was incredibly handy, which makes me mad that I learned about it only a week or two before my n900 showed up...
As far as I know there's not a good way to right click at this point because the volume keys are intercepted for volume control. That may be changed at some point; it's early yet.
As for documentation, vnc itself is pretty well documented. Keep in mind that many of the applications we have for Maemo 5 are really VERY young and many are just quick ports from source or diablo apps. Some things aren't terribly polished, but they probably will be before long. I'm not surprised that documentation is lagging behind in places; most of the people who wrote/ported the applications have only had their devices for a couple weeks or so now.