From the dollar store I get tall square plastic storage boxes 6 inches tall and a tall rectangle plastic storage box that the square one sits in - then I stuff 3 Nylon Scruffies Pads side ways so they don't float about halfway down into the square one.
Fill both with water - wash your brushes in the square side and keep clean water in the other
The dirty side stays clean because all the pigment goes under the scruffies

Body washing nylon puffs will work - Scruffies or pot and pan scrubbers for cleaning pots.
S.O.S. Tuffy Nylon Scouring Pads