Here's a video giving a little more information on how to do "the volley." Adam Winrich is using a 16-plait six-foot kangaroo bullwhip that he made himself. And just so you know, he currently holds the Guinness World Record for the most bullwhip cracks in a minute, and this is the whip he used.
The volley is best done with a well-made whip, with firm plaiting, 4-7 ft long if a bullwhip, or 3-6 ft long if a stockwhip. If your whip is really supple, like a wet noodle, or a piece of rope, you will find the volley difficult to do well.