Another way of keeping the down from getting everywhere is to do the filling in a tent... Put the tent up in the house, take the hoover into the tent, take off your clothes*, and take everything into the tent.
Once you've done the stuffing, seal the item, and then hoover up the mess.
* so the down won't stick to your clothes...
Oh, you can control the down when transferring it from source bag to filled item by stuffing it into a tube, inserting the tube into the item, and then pushing the down out of the tube. Also helps to control the amount you put in.