Now we need to make a New Art Brush for the tree branches. With the Pen Tool, make a path as shown below(1), fill with dark green, and apply the same Roughen effect as the previous step. Your path now should look like path(2). Duplicate path(2) by ALT+Drag or Copy & Paste, vertically scale it down a bit, and change it to lighter tone of green(3). Repeat this step, duplicate one more path and fill it with a even lighter tone of green(4).