The Right Brush

Square or flat brushes are generally used for painting large areas in less time.
Angle or chiseled brushes are designed to use on jobs that require cutting- into corners, painting trim, molding, window frames and sills.
Natural bristle brushes are not recommend for use in water-based paint because water absorbs into the bristles and leaves them limp. Natural bristle brushes are also not good to use on rough surfaces.
Nylon is a very durable filament and less expensive than natural bristle. These brushes are great to use on rough surfaces and should be used with fast-drying paints like acrylics since they are so easy to clean.
Polyester filaments do not absorb moisture so they retain their stiffness better than other brushes. They also resist heat so they are good to use in any climate and with all types of coatings.
Nylon/polyester blend are used in shorter lengths for stiffness when using water-based paints as well as for resistance to heat. The nylon is used in the longer lengths for precise tipping and durability during use.