Reviving Wood Finishes Most wood surfaces are protected by some sort of coating, ranging from clear varnishes on fine paneling to paints that mask the utilitarian woods of interior trim and exterior siding. Methods for cleaning them depend on the type of finish. Paint: Exterior painted surfaces can be scrubbed down by hand, or by a power washer. Interior surfaces can be washed with an all-purpose household detergent; wring out the cloth or sponge until it is almost dry. Clear Finishes: Maintain clear finishes on furniture and paneling—including varnish, lacquer, shellac, and oilby routine polishing and quick cleaning of spills….