333 Brushing Liquid is a general purpose, slow drying solvent to ease brushing and facilitate the flow of specified paint coatings. It extends drying time in hot weather, improving the flow charcteristics of enamels, varnishes, and Brightside polyurethane. See the coating can label for specific application instructions.
Physically, 333 is somewhat oily... it is not a "thin" solvent like acetone.
Brushing Liquid is also recommended in various topside systems for removing sanding residue from fiberglass and wood surfaces.