Right. Apart from the fact that washing down in a washing machine can destroy its properties if you are not very careful, that's one idea .
What birds will the down from the poultry farm come from? Down for quilts comes from geese or ducks, and not chickens or turkeys. Its a shame as the poultry farmers down would have been free wouldn't it?
Two easy ways to get enough down for a quilt are (but they do involve money) buy a cheap down quilt, or buy a couple of cheap down sleeping bags (tescos are currently selling a down bag at £39).
Sorry if I am teaching you to suck eggs here, but the fill power of down varies massively, and so you really would need to know the mix quality in order to be able to determine the end result in tog rating.
Here is a basis explanation on fill power:
http://en.wikipedia.org/wiki/Fill_power
As per above. Sorry if you knew that already....or you live next to a goose producer lol