I was worried about having down every where when I made our quilts. But it is easier to work with than it sounds. I cut the bag 1/2 way open and placed it upside down in a larger (3-5 gallon) zip lock bag. To pull it out, I reached in to the bottom of the outer ziplock, curled my hand and grabbed a handful of down from inside the Thru-hiker bag, making sure there was nothing loose, and pulled it out. Any down that may wander out of the Thru hiker bag stayed in the other outer plastic ziplock bag. The secret is not to try and pull out more down than you can control in your closed fist. I went through 6 bags of down without losing any, and it did not create a big mess.
I hope this helps,