This is for all fingerstyle guitar players and is not specific to Hawaiian or Slack.
I have a DVD recommendation for guitar players that like in depth expalnations of technique. This will show how to minimize your effort and play better with less strain. Good technique works for all fingerstyle guitar playing. Well sometimes not, but usually anyway.
BTW Kanengiser is part of a group called Los Angeles Guitar Quartet (LAGQ) These guys are very very good. Check them out if you have not heard of them. The LAGQ have a live DVD that will knock your socks off. If you are barefoot who know what could happen! LOL http://www.youtube.com/watch?v=IrPErM6-p3o