Slipshod, ice skating and roller blading are among the better cross-training activities for skiing!
Kneale Brownson is an excellent instructional resource, as his many posts across many threads confirm. I always enjoy what he has to say. Perhaps he might comment on importance of the art and challenges of teaching skiing. My understanding is that the PSIA has increased the importance of the teaching component of the L3 exam.
Over the last ten years I've had four L3 instructors over many private lessons. All were good instructors who taught me useful motions. Statistically, most L3 instructors will be within one deviation of the mean when it comes to teaching skills, eh? So I learned from all. But the latest instructor has the ability to nail just what the next step in progression is for me, specifically. The last lesson, for example, totally focused on dorsiflexion at initiation. The experience was "shazam," affecting my turn shape, balance, and -- wonderfully -- ability to hug the zipper line.
How did my instructor know that this simple motion was the next step for me? I'm clueless. No doubt, all L3's know the importance of this basic biomechanical motion. But I believe that like comedy, timing in instructing students is one key to the art. The time, then, was right.