A stencil brush is a specialist brush with short, firmly packed bristles. They are available in various widths, from small for tiny, detailed sections of a stencil to large ones for faster painting in of sections.
The main advantage of a stencil brush over a normal paint brush is that it reduces the chances of getting paint under the edge of the stencil because of the stiff bristles.
If you're painting a border stencil with several colors, you may find it easier to have a brush for each color, rather than rinsing the brush each time.
