Lacquer thinner, acetone and water rinseable semi-paste paint remover will remove graffiti, but may damage surfaces. Solvents used for removals from stained or unfinished wood may carry the graffiti into the wood surface. Remember to wear hand, eye and respiratory protection as required and safely dispose of solvent soaked wipes to prevent spontaneous combustion. A pressure washer designed to work with warm water may be helpful, but it's usually best to soften and reduce graffiti with other methods first. Be careful not to damage the surface with too much pressure.
Some surfaces require more than one coat.
Allow one coat to dry completely before applying a second coat. Save paint from an original paint job for touch ups. If you have none and have no record of the original paint, most paint suppliers are capable of custom matching of colors and sheens. Use inexpensive disposable applicators to ease your convenience and speed. Learn what is easy, cheap and effective and keep needed materials handy.