Naphtha, commonly sold as “V M & P Naphtha,” is better than mineral spirits (paint thinner) for cleaning oily and waxy surfaces, including crayon marks. Naphtha is a stronger solvent than mineral spirits but not so strong that it damages any finish other than wax as long as you don’t soak the surface. Naphtha also evaporates much more rapidly, which I find to be a more user-friendly quality. The downside of naphtha, compared with mineral spirits, is that it has a stronger odor. So it’s wise to arrange some air movement to remove the smell from the room or shop.