Put rebounders in that the keeper has to clear through. Quality and quantity are important when teaching skills. 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.