180 Grit Abrasive Cup Brush for prepping painted surfaces.? This nylon bristle cup brush is an applicator favorite, available in two sizes: 4? and 6?. Scorpion Cup Brushes are coarse grit nylon filament cup brushes that are used with air/electric polishers to scuff painted and non-painted surfaces as well as clean up rust and debris. These generally last for up to 20 truck beds. Scorpion Cup Brushes will drastically reduce prep time when scuffing surfaces and are included in most start-up packages.