This has always been a bugger for me. So I cued up my copy of Mastering the Bullwhip, grabbed a 4' whip and followed along with Anthony. It always surprises me that starting again is sometimes the easiest way to learn. I like this style of reverse crack because it allows for wonderful accuracy and keeps the whip behind you only momentarily. It is a wonderful example of stabbing vs. slashing in whip technique. I'll see if I can give you an idea about how to perform it. But to really get the nuts and bolts buy the DVD. (Look for the link on my FAQ page).
1. Lay the whip in front of you, palm down
2. Drag back and up (Slightly) with your wrist in line with your arm.
3. As your arm comes parallel with your body, stop the arm motion and flex your wrist backward sharply to about 45 degrees. The angle is key. If you flex too much the whip ends up by your ear, if you don't flex enough the whip will not continue back to crack.
4. Following the crack, flex your wrist 90 degrees straight down and move your arm forward from the shoulder to reset the whip.
That's a pretty rough description but this style of reverse crack opens up a few other little tricks. There is what I'm calling "The Delongis Flash". A forward/back horizontal into a diagonal overhead continuing the line. A nice trick when you pull it off. And then a back/front underhand to forward gypsy. These multi-cracking sequences will increase your dialogue with the whip and allow you find how the whip works with you. Did I mention the crack was accurate? Stay Safe, Practice.