I've thought about it a great deal, and discussed it with a variety of people, because the orientation of the hand can make moving the valves easier or quite a bit more difficult.
For the right post, which for me is very easy, I grip the handle with its long axis across my palm, thumb under and fingers over, as you would grasp a baton. I can close and open the valve with wrist motion. For the isolator, I use the same trip for closing, but I roll the valve to open it, because that motion doesn't work very well for my wrist.
For the left post, because of the directions involved, I try to grasp the handle with my fingers and use forearm supination to close the valve. It's far more difficult.