Selecting painting brushes involves considering the types of brushes available, such as round, flat, filbert, fan, detail, and angular. Bristle material is also important, with options like natural (sable, hog, squirrel) and synthetic (nylon, polyester) affecting quality and durability. Factors like ferrule construction, handle material, bristle loss, shape retention, and intended medium (oil, acrylic, watercolor) should be taken into account to ensure the right brush for the job.