I scrub my horse hair brushes against each other in a bucket of lots of dish soap and hot water. Its best if you can use rubber dish-washing gloves so you can have really hot water. Then I spray them with mouthwash/Listerine and let them sit in a dry bucket or towel, bristles down. Mouthwash can be poured into a spray bottle and it is a cheap disinfectant. It will not dry out wooden brushes like bleach will. Later that day once they have sat out I give them a final rinse.