Reference: Natural Media Brushes library
This chapter contains descriptions of brush categories included in the Natural Media Brushes library, as well as sample brushstrokes. The Natural Media Brushes library makes it easy for artists to transition from traditional to digital art. It gives quick, one-stop access to brushes that mimic traditional media, from pencils and pastels to oils and acrylics, and much more. If you’ve used it in the real world, chances are you’ll find the digital equivalent in the Natural Media Brushes library.
The Natural Media Brushes library is available for download from the Welcome book store (Help 
Welcome Store.)
To access the Natural Media Brushes library, first download it from the Welcome book store. Next, restart Painter, and then in the Brush Selector, choose Natural Media Brushes from the Brush Library list box.
To choose a brush category and a brush variant, in the Brush Selector, choose a brush category, and then click a brush variant.