Hand grab animation with Vive triggers

So basically I'm trying to figure out how to animate the players hand models when you press the trigger on a vive controller. Depending on how far down the trigger is pressed, the more "clenched" the hand will be. I figured the best approach would be to get the axis value of the trigger input by setting it to a float, and setting a float parameter in the animator for the hand animation, however I can't seem to get this working. Both hand models are also rigged.