I've tried washing my goose-down pillows in my washer to no avail. They always end up smelling moldy cause it holds the moisture, regardless of how long I dry them.
I have a king-sized goose-down matress and had to have it sent away. It only cost me $30 (which is a miracle, considering how huge it is) and they delivered it there (they had to take it to the Cities) and back.
If you're like me and leary of the chemicals they use to dry-clean garments, there is a place called Nature's Best Cleaners that uses "green" cleaners/technology. I've been going to them since I was in high school, and they've always been fantastic. I'm not sure what's in your area, but there's bound to be a dry-cleaners near you that can accommodate your comforter. :)