I washed a cashmere sweater by hand one time and regretted it. It just wasn't the same.
However, with the same sweater, I washed it again, only this time I used Nikwax Wool Wash. I had nothing to lose. I swear the sweater has been rejuvenated. I even washed it in the machine on delicate. I air-fluffed it with no heat and laid it out to dry. I normally wouldn't recommend washing a cashmere sweater, but I did see how Nikwax rejuvenated the sweater I previously washed and ruined in another well-known American wool wash.