First thing we got to do when we're done printing is wash out the screen. Black inks can stain the screen, leaving a ghost image. If there are too many ghost images, the screen will start to clog.
I grabbed the Ajax soap from the kitchen sink and brought my screen, soap, and scrubber to the hose to wash it all out. The inks I suggested are water soluable so they're totally safe to wash out in your yard or down your drain. The emulsion is hard so don't be afraid to scrub. However, older screens can rip if scrubbed to aggresively.