Teaching Single Versus Dual Intent

I had an inquiry about teaching single and dual intent for battery and I want to appeal for your collective wisdom.  About the time I started teaching there was a robust list-serv discussion on this topic that I found helpful.  Given that the ALI is working on the Restatement of Intentional Torts right now, many of you may have thought about this recently.  I take the inquiry to be more about pedagogy than doctrine, but all tips are welcome.  How do you teach single versus dual intent?  How do you integrate it with purpose and substantial certainty?  Do you recommend any good sources for students?  Thanks!