Soak the jacket in water and add in diluted down cleaner. Continue to let it soak for 5 minutes; clean the dirty part with a soft brush. Squeeze out the water, then rinse and soak the garment in clean water. Repeat this cycle 3 to 4 times until the garment is thoroughly clean.
Remove fur collar and accessories from the jacket; zip up and snap all velcros before putting it in a laundry bag. Launder with two bottles of down cleaner (for washing two garments) on gentle cycle. Do not use any detergent with bleach or softener as the chemicals will damage the down clusters.
Spin dry on high speed in the washer for 3 to 5 times, then dry the garment in an automatic dryer (in accordance with the instructions on the washing label). Toss a tennis ball in before the drying cycle begins as it is ideal for fluffing up the down clusters. This method might not be suitable for down jackets with light-color or very thin outer shell. After drying for 5 to 10 minutes, fluff and pat the down inside by hand and then put it back in the dryer. It takes a long time to have the down jacket dried completely, but repeating this process is the best way to retain the fluffiness of the jacket.
Professional Cleaning (The best method)
The best way to clean a down jacket is by a professional cleaner as they have the experience and expertise in cleaning down items.