We suggest hand washing with a gentle detergent and laying flat to dry. Aggressive rubbing can clump the fine down, so we suggest “patting” rather than “scrubbing”.
If there is clumping, you can put it in the tumble dryer on a light quick cycle with 2-4 tennis balls. Otherwise just give it a good shake and pat.
Make sure it is bone-dry before storing.
It is also suggested not to over wash your jacket. For spot stains (particular oil/ fat) dishwashing liquid works wonders!