Carefully brush off as much hair and dirt as possible. I think the rubber sponge for cat hair or felt pads is best. Available from 5Star or a pet supply store. You don't want to fray the yarn with a brush. If you don't have a rubber sponge try a cellulose sponge. Then rinse with lots of cool running water. If very soiled a 30 minute soak would help. If very very dirty soak in a teaspoon of Downy with at least 3 gallons of water for 30 minutes and rinse extremely well starting with a soak in clear clean water again for at least 20 minutes, then clear running water. Soap in their garments makes them unhappy.