I once asked one of my teachers about some of the more flambouyant twirling moves with staffs, and he explained that they were often separate applications practiced together in the form. So you practice the big overhead spin with the palm open (which I must agree, I've only done with a horse cutter), and you're actually practising 2 grip changes. The advantage of this is that it's harder, so you become better at doing the small grip changes. It's the same with a lot of the big overhead twirls, they're really little hooks and digs linked together to give you a better feel for the energies.
Hate to disagree with you David, but I could teach for 3 hours on bow applications.