BRUSH BASICSStiffness Stiff Designed to create sharp lines when cutting in around edges and corners. Popular stiff brushes: Medium Stiff Combines precision of the stiff brushes with a smooth finish of the soft, making them a versatile choice for any project. Popular medium stiff brushes: Soft Designed for fine interior work, soft brushes deliver a smooth, brush mark-free finish. Excellent for satin and gloss paints and clears. Popular soft brushes: