I have a Goshman sponge hand that I baught from David Ginn. The trick requires you to invert the hand inside out so that it looks like a sponge ball. I can do the inversion, but I am having trouble with re-inverting it. Youa re supposed to stuff it inside your fist really quickly and press in so that it turns inside out again. I put it in my fist but it doesn't do that. Does anybody have any tips or suggestions for me?

I have found with the Gosh reversable stuff (hand, bunny, giant ball etc) that making sure it gets a sniff of water before performance keeps it puffed out and more willing to take its shape.
Also, have you tried checking your position on the finger and thumb (open'ish fist) to make sure that when you push it your fist, it reverses properly? e.g. that it 'grips' as the wall of the ball hits your hand. I'm no 'big sponge' expert, but remember it being a bit 'knacky', a case of finding the right hand position.
Good luck!

Hmm, I havn't really noticed anything abnormal with it. I might check it again to see if I am even folding it up right lol.

I also bought one of those from David Ginn at a lecture he recently did for our club.
He said that he would go into a rest room right before a performance and soak the hand in water, then wring out all the water. He'd repeat this several more times, then set it up into the proper position & place it in a qt. size zip-lock bag until needed. Haven't used mine yet so I don't know but he did great with his!

Sir Richard.