For the fashion-forward, wool hats make a fabulous addition ... work it in with a toothbrush or felt sponge. Washing wool clothing with vinegar is a common cleaning practice because it's also ...
If the hat doesn't say Dry Clean Only, do a spot test to make sure ... a hat with a loose weave probably won't be as strong as a fine weave. For felt, try this method from Fashionable Hats.