Rather than "using the turn to slow down", think, instead, of using the SHAPE of the turn, and especially the END of the turn as the way to control your speed. Let your skis float into the fall line, enjoy your moments of hanging out there, feel the rush, THEN, gently steer the skis into the finish of the turn, and FULLY COMPLETE the turn so you're almost turning up the hill again. Once you feel yourself begin to slow down, then it's time to start the next turn.
By speeding through the belly of the turn (skipping the fall line), you're having to use your muscles to slow down, and you're most likely to over rotate your entire body, getting "stuck" in the turn, which makes it super difficult to start the next turn.
Take a moment and rewatch those videos with that mind set and try to "feel" what he's doing in the middle and end of each turn. Watch the patience he displays in each and every turn.
It's really is like driving a car - slow BEFORE the turn, start the turn, accelerate into the belly of the turn, and back off the accelerator at the end. Zoooooooommmmmm!!!