Had a call off my good lady wife last night while I was at work. Nearly in tears, she told me that without thinking she had put her down jacket in the washing machine along with a synthetic gilet. At the end of the wash she took out the gilet, which was ok, and then saw the clumped and clotted mess that was her pride and joy.
"Don't panic", I told her, then she was worrying a; the jacket would be ruined, and b; I would be upset because I had bought it for her. She was using "Tech Wash" rather than "Down Wash" (I'm convinced they are the same thing.)
I told her to leave it in the machine, still damp, and I would sort it out today before my next shift.
I inspected the jacket and it was severely clumped up, the down was in hard white pellets inside the baffles but there was no damage anywhere, so I opted for radical action. I just set the dryer to low, then added a clean trainer, and set it off.
Fifteen minutes later I did a check and it seemed to be working ok, then after 45 minutes I stopped the dryer and pulled the jacket out. I was pleasantly surprised to find the jacket as good as new, clean, and with the down lofting properly. Big kisses from Mrs P too.
I know the advice is to use a couple of tennis balls, but I don't have any. Some years ago when there was a down cleaning business near here the owner told me about the trainer trick, seems he finished all of his clients down gear with a warm tumble dry and a training shoe.