Interesting thread, still going nearly two years later.
Bob Barnes said it best in post #115.
Balance, as always, is huge. Ski centered, shin touching the cuff but not driving the tips down. This places you in a position of control and allows you to drive the skis through variations in density.
Although the edges are not engaged to a firm surface, the angle of the ski relative to the snow controls your platform and it is still necessary to release to initiate a new turn. Hence, my signature, in all conditions.
Down or up unweighting, while a fun enhancement to anyone's powder skiing, is not necessary. A ski tipped toward its downhill edge will still drop nicely into a turn, even if it is buried under 3 feet of snow. Attempting to teach bounce to a new powder skier adds movement complexity. Teach patience. Use patience in teaching, too. Tip the ski, allow the turn.
Powder turns will be longer. Tail follows tip. Resist the impulse to push the ski into the turn. Guide, don't twist. Patience.
There's more, of course. This is just a start, which I believe was the subject of the OP.
"Bouncing" or unweighting of various kinds can be useful, effective and fun, but it's not necessary when you're still trying to figure out powder for the first (or third) time. Relax, tip the skis, let them turn. With unweighting (retraction is my favorite) it is possible to guide the tips more aggressively, but you need to be ready to balance the forces that a more rapid change in direction will generate.
FWIW (not much), my first powder was at Berthoud Pass on a pair of 203cm Omesofts. Narrow by today's standards, but a reasonable choice for powder in those days. Since then, I've skied a fair amount of powder. The most I've ever skied on a "narrow" ski was 3 feet of untouched on a pair with 78mm underfoot. Since then, I've gone wider, using 96mm, 106mm and 115mm at various times. My daily driver in a place known for powder is 96mm. In my avatar picture, I'm on a low angle slope wearing 78mm skis.