Put aside one set of brushes (1" and 2") for chiseled edge work only.  Don't use these to pound or beat the canvas (like for tree and bush underpainting).  Bob Ross brushes are made of natural bristles so they do break with hard use.

When loading the brush to a chiseled edge, hold the brush at a 45-degree angle and wiggle gently through a large amount of paint.  The key to this technique is having a lot of paint on the brush.

Tip from Bob Ross Inc.