Ahhh yes there is a way to do this. Nikwax do a product called downwash which you can use in your regular washing machine. However for drying them you either have to put them on a horizontal drying rack and turn them frequently or take them to a laundry/ somewhere with a large tumble dryer and tumble dry them with a tennis ball to stop the down from clumping. Did mine not too long ago for the first time and it worked really well. There are of course official down-washing places, but these probably cost loads!
Have a look at:
http://www.nikwax-usa.com/en-gb/products/productdetail.php?productid=2
Darren ap Dafydd (Welsh Rambler)