Better than using expo try setting a low rate setting. When you set expo it still has full travel if you move the sticks completely to one side or the other. Expo only changes how the control surface moves at less than 100% control throw. But if you set a low rate in (using dual rates) then you will reduce the total amount of throw. This will work a lot better for helping them overcome over control on the stick. With expo in when the move the stick all the way to it's limits you are still going to have the same amount of control throw on the control surface regardless of how much expo you have dialed in.

Ken