Way back in the old days, Frostline kits would send the down in muslin sleeves that fit inside the baffles. You would then put the open end all the way into the baffle, push the closed end (essentially turn it inside-out and carefully pull it out of the baffle. It still was messy but most of the down did end up in the baffle. I bet Frostline wet the down to fill the bags and then sewed them up and put them in a dryer to fluff up the down. Just a guess.