A perfect example is a freeway sound wall or any cinder block wall. Eventually, every panel will be painted so the entire wall will have the same appearance. Cites that can invest in scientific methods of graffiti removal will benefit from products like those offered by CompuColor Graffiti Systems. Using spectrophotometers, CompuColor can match the color of the existing wall and mix paint on the spot for immediate coverage. Our city has experimented with pressure water washers, washers that use water and sand, and the wire brush.
Pressure washers can actually etch a cinder block wall, further hastening the wall's demise.
The wire brush is limited in effectiveness as well. Pressure washing never completely removes the vandalism because of the porous surfaces involved. A hazy remnant of the graffiti still remains. Elbow grease and the wire brush. An inexpensive wire brush is excellent for removing paint from many surfaces.