It sometimes seems to me that riders have less control over their whip than they do over their horse. The whip will swing around or flop or hang at odd angles. Even the quietest hand can drop the whip, usually at a distance in inverse proportion to the mounting block.
What many people don’t realize is that the handle of the whip is not where you want to hold it, despite all the appealing materials of leather, suede, chrome and brass that go into finishing it off. All that pretty stuff is alluring in the tack shop but not of much use in the saddle.
You usually want to hold a whip at its balance point, which is where the weight of the portion above your hand equals the weight of the portion below your hand. That way the whip can align across your thigh, rather than dropping down toward the shoulder, so you can use it with subtlety to back up your leg aids. It will also help the bottom of your hand to stay flat and not be pulled to an angle by the weight of the whip.
The balance point of a whip usually is located where the handle attaches to the shaft of the whip so that your hand should cover the ferrule, that metal thingy at the bottom of the handle. The weight of the shorter/thicker handle, in most cases, equals the weight of the longer/thinner shaft.
I hate it when I have to mess around with the balance of the whip in my hand, and I love the idea I got years ago (thank you Carole Martin) to slide a rubber rein stop up onto the whip to keep it in place. The rein stop sits just above the balance point and thus just above your hand. You can open your hand or adjust the reins and the whip just stays right where it needs to be. You can pretty much forget about it.
I have friends who’ve loved that rein stop idea and others who hate it, usually saying that it gets in the way when they change the whip to the other hand, although it’s never bothered me for that. I can usually tell which whip is mine when lined up on the wall because it’s the one with the rein stop, and I don’t have to worry about other people borrowing it and then forgetting to put it back.