Stroke a path
Make the bubble look hand-drawn with an edge that varies in width
To start off, add a new transparent layer to the top of the stack. Select the Brush tool, and choose a Round Point Stiff Bristle brush tip. Set Size to 50. Set the foreground colour to black. Click on the Shape 1 layer. Click on the Paths panel. Double-click on the Shape 1 Shape Path thumbnail. Click OK in the Save Path window to create a copy. Click back on the Layers panel. Click to target the new transparent layer. Click back on the Paths panel. Right-click on the Shape 1 Shape Path copy and choose Stroke Path. Set the Tool dropdown to Brush. Tick Simulate Pressure. Finally, click OK.