I am a former paint chemist and dealt with wood coatings and automotive finishes- use mineral spirits on a test panel. Don't bath the car in mineral spirits, but spot wipe where the damage is done. Most wood coatings that are solvent based are made with mineral spirits, so it should dissolve the overspray. Keep in mind you will be removing any coat of wax you may have so get ready to get a coat of wax on as well. The mineral spirits shouldn't hurt the auto's urethane as long as your wipe it off quickly. Aliphatic Naptha works well also. Just test an area first for safety. Have one rag for the solvent and one for drying (wipe on and wipe off Danielson).