If the left hand were a fist, I'd have reversed it for that reason.
Turning an open hand into a fist is far easier than a fist into an open hand (although that can be done too).
My preference is to use a wooden block when doing this... Apply pressure first to the finger tips, so they curl inward. Then just work you way down the hand. Apply pressure to the top and bottom of the hand to squeeze the fingers together. Finally move the thumb into position.
Sometime the fingers resist curling, so making a small shallow cut behind each knuckle will give them room to compress (a jeweler's saw works better than a scalpel for this). Also, needle nosed jewelry pliers (available at places like Hobby Lobby and Michael's) can help with stubborn fingers, but if you aren't careful you will mar the metal. A pair of padded regular pliers can be used, but the chances of one finger going the wrong way, or just crushing the whole hand is kind of high. If you use padded pliers at all, I would recommend them for when you are squeezing the fingers together.
But this is all from a "It could be done" point of view... As I've said before, I love the pose and really do hope you paint it and post pictures.
Caz
