Flats hold a large amount of paint and are useful for blocking in large areas. Mops have a large quantity of soft hair for moving a large quantity of paint in a loose manner and blending wet areas. Mops are best used for wetting paper and painting large, soft, fluid passages such as skies. Lacking a sharp point, Filbert shaped sables are great for foliage work due to their oblong blunt ends.
Fans are flat pie-wedge shaped brushes used for blending in oil or acrylic painting.
The bristle fan is good for scrubbing out linear strokes in watercolors. Most professional watercolorists use a selection of rounds and flats, red sable brushes. The most sought after and expensive soft haired brush. It is traditionally taken from the tails of the sable marten, a member of the mink family. The finest grade of brushes are hand made from Kolinsky red sable and are quite expensive, but with proper care, cleaning and storage, can be a lifetime investment.