In Motion, off the top of my head, you'd draw it out with the Bezier tool. Turn off Fill, make the Outline "Airbrush". You can apply a Randomize parameter behavior to the Outline's Width parameter. Then in Stroke section of the Inspector, you can open the Width Over Stroke section, and make points to make parts of the line thicker or thinner. Other various parameters may need tweaking, but it's all pretty easy to do once you get started. Very quick, fairly easy.