Here is how to change Appearance of Brushes !
Assuming that no Brush palette is open . Go to Window>Brushes (short cut F5)
Click on the small arrow on the window panel of Brushes > Open Brush Library> Other Library to browse to a new brush file or the brush set already loaded .Here is a screen shot.
Draw a line , apply the brush from the new library , you will notice that it will appear in the brushes pallette.
Double click it which will open Art Brush Options window.
click on Flip Across or Flip Along to see brush change its direction.
Brush Change Alert will open Click on apply to Stroke!
Credits :- I have used Ornate Brushes in this tutorial.