If you haven't followed any of Ackman's shorts, they are a lesson in business if nothing else. Even sitting on the sidelines and not shorting with him, the depth of research and the thoroughness are an impressive lesson on how much research should really go into an investment. His 342 slide presentation on the topic is impressive and Ackman has outlined all of the details on his site Facts About Herbalife.
I would imagine $HLF uses some of their $350m cash to try and buy back shares and convince others not to short or at least try to make it painful for Ackman to stay short. I doubt anything they do will shake Ackman though as the profits are going to his charity and he is well known for staying in these incredibly researched positions for a long time.