Wash your down items in the washer, dry in the dryer.
They don't usually need special pampering, and you are not concerned with the fabric shell on your thrift store down score, however, buying and using some down detergent instead of regular will help refresh the down better and help with bringing back the loft. You can find down cleaner in lots of places, I found mine at an outdoor shop that sold down bags.
If you don't use down detergent, don't use too much regular detergent! A little bit will do.