This has to do with your first question:
My first down project was an underquilt for a hammock. I borrowed a friend's large shop vacuum and built a "down eductor"(search BPL) out of PVC plumbing to blow the 750-fill down into the channels.
The eductor worked OK but was a pain to set up and to clean up errant clusters later. It also once backfired on me. I recently made a 900-fill baffled summer quilt based on Jamie's design but opted to use nothing more than a paper towel tube with Nanonseeum mesh on one end. It worked very well!
First, suspend your sewn quilt from its corners as Jamie illustrates. Gravity and open channels are your friends here.
Lay two pieces of Nanoseeum mesh on top of a paper towel tube's end, one layer 45 degrees off from the other. Tape these down with any decent tape. It's a good idea to tare out the weight of the tube on your scale, or at least weigh it and write on the side of the tube with a Sharpie.
Place your 3oz bag of down in a *PAPER* grocery bag. I found that the paper bag had low static cling, so the loose down clusters would gently settle on the bottom where I could reclaim most of them later.
Open the top of the down package and stick the open end of the cardboard tube into the opening and use a couple fingers on your free hand to stuff the down up into the tube. You can get at least 35 grams of down securely into the tube.
Transfer the tube to on top of your scale, open end facing down. It will stand upright. Weigh it.
When you're satisfied that you have enough for your channel, stick the open end of the tube into it, gathering up a good length of the channel around the tube and sealing with one hand. Blow with a quick, short breath against the mesh end and the down will blast into the bottom of the channel. You can now roll the hem on this section and clamp with a paper binder.
I filled my quilt with 7 ounces of down in about 20 minutes. Clean up was a matter of rolling closed the top of the paper bag. I may have chased two down clusters, but that was it!