I lay my thumb on the bottom of the trackpad and hold it down, then my pointer is free to drag, lift away, reposition, and drag more. It's extremely convenient and certainly one-handed.
The trackpads are also multitouch, so they handle multiple hands as sensibly as you might expect.
> I lay my thumb on the bottom of the trackpad and hold it down
That's an awesome tip. I didn't know that the Apple trackpads would do that. They're less reliable if you just try to throw a second finger into the mix, which seems to generally lose the drag and turn it into a secondary click scenario. The bottom of the pad seems to be special-cased to avoid this.
The trackpads are also multitouch, so they handle multiple hands as sensibly as you might expect.