You don't want to have a keeper in a drill so long that they're tired and can't do anything but get hit. Groups of three or four work well as far as getting good repetitions and staying fresh. You can have them take five to ten balls and switch out, or recycle them so that they go one after the other. Movement is important. Keepers need to be able to play shots from a static position and shots as they're moving.
Footwork is critical in determining how a keeper can play a ball.
How a keeper plays a ball is going to dictate what he can do next, i.e. recovery. A keeper needs to be able to play the second shot. When you think of all of these elements, there's a lot to reinforce. It's important to use the resources available to you when working with beginning keepers. We might not have a ton of hockey balls, but we probably have a tennis racquet and a ton of balls, we probably have a soccer ball.