The way to learn a hs bs 3 is by learning a bs 180 from the inside of the wake to the outside with the handle pass. After you master that, try edging out on your heel edge and doing a bunny hop bs 180 with a handle pass. After you can do both of those you are ready to do a hs bs 3. Just go into the wake with a consistent edge (opposite of a raley cut), starting about 15 ft out, and once you hit the wake pretend you are doing the inside out bs 180, I guarantee you will overrotate and do a bs 3- and you will have the handle from learning how to get it on the bs 180s you practiced before.
good luck, you shouldn't have too much trouble. If you want to see one, I do a couple in this video- http://photos.wakeboarder.com/showphoto.php?photo=11444&cat=508