Here's a few tips on Using the Dressage Whip Effectively from the Good HorsePerson:
1) Grip - Find the grip that you like best - thick rubber has a lot of stick-tuiveness but it's heavy. Leather over fiberglass is lightweight but can be slippery. Rubber spiral can be a good intermediate choice for grip without bulk.
2) Topper - Do you like the gleam and solidity of a big metal topper, or does a light plastic little mushroom feel better? It's all about how comfortable it feels in your hand with the rein. A topper is absolutely necessary to carry a whip properly - without one, you have to grip the whip too hard to keep it from sliding through your hand and you will end up compromising the feel of that rein.
3) Length - Let's face it...a tiny person on a huge horse needs a bigger whip, it's all about proportion. The whip should point at a forty-five degree angle - the lash should point below the hip bone of the horse and just above the corner of a square saddle pad. Don't forget the relatively new length rule for dressage competition - you might have to swap your schooling whip for a shorter one at shows, or you might be able to trim off the lash to make it fit.
4) Flexibility - Find a whip that has the right "snap" for your horse - a really stiff whip won't give as big of a bite and is easier to control (probably better for sensitive horses). A whip with a lot of give will give bigger bites when you really flick it - probably best for Joe Slow or warmbloods with thicker hides or duller brains.
5) Weight - this aspect is last, because if the other four are suitable to you, weight will probably be also. But it's good to try lots of different whips - the material and shape of the handle and body affect how the whip balances in your hand. If you feel like you can hold it with little effort, it's probably a good choice.
Finally, if you feel like you have the perfect whip, but using it is still not coming naturally, check your hand position and "flicking style." If the whip is hitting too high or too low, your hand is probably improperly flexed at the wrist. Try letting your hand fall naturally from your wrist and resist the urge to twist it to move your horse's head position, instead, shorten the rein or move your arm slightly. As for flicking style - again, check the wrist flexion while flicking - just turn your outside knuckles out momentarily and then "close that little window" by snapping your wrist back into position with conviction. Concentrate on this action and let the result be that the whip hits the horse. Resist the urge to move your arm back or to open your arm/elbow away from the body. Soon you will be super subtle and the whip will be your extra appendage!
