thanks for the really helpful replies, guys!
I guess my idea of "dynamic riding" was limited by a youtube video (might have been snowolf's) that i watched, talking about how your upper body moves down the fall line in a fairly straight line while your lower body twists and you flex your knees accordingly (sort of like the "Tall and Small" example in one of your blog articles, Jed
all this talk made me realize that my body position is a separate issue from dynamic riding. I've only been on a snowboard for 10 days so far (the first 3 of which were wasted falling all over without proper instruction), and i'm probably facing forward on blue/black runs because I'm still not used to going sideways at speed. I'm getting into park stuff as well, so I'll continue riding duck and see how it goes.
I'll have to get comfortable with going sideways down blue/blacks first, but I will also practice what stillz/Jed mentioned on greens in the meantime! I've been doing a bit of unweighting and forcing faster turns (i think), but the fore and aft movements is new.