This is usually the revenge tactic of a disgruntled cat, not too happy about your project.Anyway, here goes- wash with Murphy's oil,dry immediately. Then use a citrus product such as ODOR-BAN. This is a concentrate that is diluted and sprayed on with a spray bottle or garden sprayer. It's used to eliminate odors. We got our's at SAM'S. When all else fails prime with Bulldog or Kilz (paints.) Good Luck.