First, I would never use water on natural bristle brushs. The way I
clean my brushs after a full eight hours of use in oil base primer or
finish only takes a few minutes and never leaves them hard. Begin by
filling a 1 pound coffee can about 1/3 of the way up, then dunk the
brush repeatedly in it, next use a wire brush or comb to remove any
heavy dried stuff or paint inside the brush. Finally, spin the brush for
several seconds. Repeat these steps three more times with new thinner
each time, then replace the brush into it's holder or shuck