I wouldn't necessarily recommend using the bone tool, its sort of grumpy and doesn't like to work. In fact it can even crash the program, despite how much memory its actually taking up.
The bone tool to me is more or less a rendering thing. Like, animate what you want with the one tool, and then convert those frames to a frame-by-frame animation.
As far as the motion tweening goes with flash, you basically can get the same effect without the use of the bone tool. Just play around with the axis points and you'll have a basic skeleton.