How do you clean Powder Brush #1 (natural brustles)?

I always run the brushes under warm water. Then I squeeze a drop of liquid hand soap onto the bristles. Squeeze the soapy water through the bristles several times. It is very important to always rub the bristles in the direction away from the handle. Do not splay or pull the bristles out of alignment. You may have to do the warm water, soap sequence several times before the brush comes clean.
Washing your brushes more often will help you to clean them easier.