Ron,
J. C. giving you some great advice here.....
It's a good suggestion by J.C. to visit the Harb ski system website as there are a lot of the PMTS lessons for green-slopers there which are really easy to follow.
Try:
http://www.harbskisystems.com/lessonindex.htm
If nothing else, the phantom move is the bread and butter of PMTS and , as HH says, even if you don't do it well, you'll still get immediate and postive results......
I think the advice of sugar-coating is a pretty good tactic......I found kids will give you all they're got if you are meeting Their needs, treat them with respect and keep the fun-level dialled up..... and what could be more fun than skiing!!.......
Good luck with the 13 year old.
Bluey