I'd make "hands" out of furniture foam. It's sold in most of the larger fabric stores. stack crossection layers on top of eachother and glue them together with spray-adhesive. Then sew a glove over top of that. You can pin the fabric together on top of the glove inside-out, then sew it up, take it off, then turn it back inside right, it should go on the other hand, and the seams will all be hidden. For that to work, you must make sure the hands are good mirror images of each other.
Cutting furniture foam can be a little tricky. Hot-wire cutting tools work best, but with a bit of practice, you can make due with scissors and sharp knives. Since none of the foam will be visible, you can pretty easily fix your mistakes just by gluing on more pieces of foam.
You can either slice a slit in the middle of the hands and just let friction hold them in place, or you can hollow out a core and fix some sort of handle in place. Personally, I'd try doing the slit first, and if that didn't hold well enough, I'd look into trying to install a handle. Though, if you fit the handle in place as you stack up the layers of foam to make the hand, you could probably anchor the handle much more securely. PVC pipe or a wooden dowel about 1'' in diameter should do the trick.