Polyurethane brushes are widely used on hardwood floors because it lasts longer than other finishes like varnish or shellac due to polyurethane composition. It’s flexible enough to resist cracking when dried paint is pulled or rubbed. It’s also water-resistant, so you can easily clean up spills without damaging any finish on your flooring. 1.Wooster 5221-2 brush 2.Wooster Brush 3103-1 3.Magimate Paint Brushes 4.Bates Paint Brushes 5.Pro Grade Paint Brushes