In the Layers palette, click on the Create a New Layer icon to create another new layer and, again, switch back to the Paths palette. With the new path active, press-and-hold the Option key (PC: Alt key) and click on the Stroke Path with Brush icon. In the Stroke Path dialog, choose Brush from the Tool pop-up menu, if it is not already selected, and turn on the Simulate Pressure checkbox. Click OK and the brush will paint along the path (on the active layer).
You can also build on this technique by smudging the border. To do this, first choose the Smudge tool (R) and then enter the settings you want in the Options Bar. (Here you can see the settings I used in this example.) Activate one of the border layers, switch to the Paths palette, and make sure the path is also active. Press-and-hold the Option key (PC: Alt key) and click on the Stroke Path with Brush icon. In the Stroke Path dialog, choose Smudge from the Tool pop-up menu, if it is not already selected, turn on the Simulate Pressure checkbox, and click OK. Here’s the result after applying the smudge along the path twice.