1. Create an Art Brush
Use the
Pen Tool and create a path like the image on the left. Drag it to the
Brushes Library pallate. If your
Brushes is not showing, go to
Window > Brushes of press
F5.

New Art Brush
When the
New Brush options window popup, select
New Art Brush.

Art Brush Options
Then the
New Art Brush Options will pop out, leave everything as default, but select
Tints for
Colorization Method. Click Ok.

2. Apply your strokes
Now you can apply this
Art Brush to any stroke by clicking the Art Brush in the
Brushes library.

Bonus Tips
You can change your stroke color and weight to get various stroke effect.
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