How about some chandelles? They're part of the commercial curriculum but they're a good test of flying coordinated and getting comfortable with rudder use. For example with a chandelle to the left you're going to start out with left rudder and transition to right rudder by the completion of the turn in slow flight. I don't remember any of my students having a particular 'aha' moment with using the rudder, just a more gradual mastery with experience. Best of luck and don't tell your instructor you went to the internet for advice
http://en.wikipedia.org/wiki/Chandelle