To remove graffiti most effectively a 3000 psi pressure washer that can heat the water to approximately 190 degrees at a 5 gpm flow is most desired. If you have access to a cold water pressure washer (1500 - 3000 psi) you may want to extend the dwell time of the chemical on the surface to a minimum of 20 minutes. If only a garden hose is available, apply product to the surface, let stand for 10 minutes, agitate with a medium nylon bristle brush, reapply product and let stand for another 20 minutes. Using a jet stream from the hose, working from the bottom up, wash off the graffiti.