I read somewhere that some people use a turkey bag for cooking when they use heated water bottles to roll a temple ball. So I thought that if the turkey bags is big enough to put as bird in, then the end of a bubble bag should also fit. If that is so then tying a bubble bag, so that the turkey bag hangs below it, then doing your sift in the bag, should allow 100% of product to end up in the bottom of the bag. A second advantage to this would be to use the hot water bottle method to process the fruits of your labour into what ever shape you want or just get it out of the bag.
I do it for the same reason but it is nice when you want break from flower.