I've heard that quite often when you take things to the drycleaners to have them drycleaned they often wash and dry them rather than drycleaning them with chemicals.

what the drycleaning place has that you probably don't, however, is big commercial washing machines so that they can fit your king size down duvet into it whereas you might have trouble using your washing machine at home or even the commercial washers that you find in laundromats.

so i guess you can do it yourself if you have a washer / dryer that is big enough for that... but it might be a safer bet to get it done at a drycleaners.