Mostly they used lye and ash and dirt to get out spots. They used solvents like turpentine and male urine also. Actually wool can be washed if it has been properly shrunk in the construction stage. I remember reading that the scots boiled the wool after weaving to make the kilts water proof.

My husband has a couple of expensive wool blankets that cost $100 to dry clean. He couldn't tolerate the price so washed the lesser favorite one on cold, gentle cycle using woolite. He hung it outside to dry. No difference that you can see, but it felt softer and smelled wonderful. He then washed his favorite.

I still think it's itchy. I prefer goose down comforters. Just as warm and much lighter.