Although by default each stroke has a unique brush attached to it, you can force strokes to share a single brush. When strokes share a brush, any changes you make to the brush affect all the strokes that brush is attached to. This is particularly useful if you have many strokes sharing the same look and behavior, for example, the strokes used for hair on a head.
When you attempt to share a brush with several strokes, the stroke attached to that brush must have been the last stroke selected. (The stroke last selected is also called the primary selection object and highlights green by default.) For example, if you want to share the brush attached to strokeFern1 with strokeGrass2, strokeGrass3 and strokeGrass4, you must first select the three Grass strokes, then select strokeFern1.
To make strokes share the same brush
When you modify the attributes of this brush for any one stroke, the changes are reflected on all the strokes sharing that brush.
To remove brush sharing
Paint Effects creates a new brush for each stroke using the settings of the shared brush. For example, if you remove brush sharing from three strokes sharing a brush named ferns1, the first created stroke retains the brush named ferns1, and new brushes named ferns2 and ferns3 are created and attached to the other two strokes.