At Chicago last Saturday, Teresa shared a great tip for brushing the back:
If you have the Total Workout or Tempo Arms, you are using the "tricep stretch" technique--where you hold the brush, for example, in your right hand, bring it across, over, and behind your left shoulder. Using your left hand, push gently on your right elbow, being careful to keep elbow level with shoulder and shoulder not hunched--a bit tricky with holding the brush and trying to brush vs. just "patting" on your back!
Then repeat with the other side. Now you not only got your upper back/backs of shoulder blades brushed, you did a nice tricep stretch at the same time!