Use regular dish soap!! It has the ability to be gentle on your paint brushes while removing the sticky, slick paint behind. Fill a small cup or jar with regular (non-foaming) dish soap so it is slightly deeper than the head of your brush. Mix your brush in the soap, coating as many bristles as possible. Remove brush and wipe on a paper towel or newspaper. The soap gives the paint something to stick to and will be left behind on the paper towel. Just repeat until your brush is clean!