let them sit in bleach then clean them well with dish soap

Dishwasher works or you can buy this Brush Cleaner from SmartPakequine

Dishwasher..... works every time

First, take a curry and try to get lots of the hair off. Sometimes a hoofpick helps with this. Then, since the brush is wooden, use a hose and soap and try to clean it. It may not be perfect, but it should be a start.

@tamarajongmans do you have wooden brush or plastic?

I just throw them in a bucket with hot water and add some antiseptic/antibacterial stuff to kill germs and fungi. I leave them in the bucket for a few hours, rub them clean and rinse with water.