How do I draw in a marker pen style?

Piranesi includes marker styles from wang wang.

Wang Wang is an accomplished Piranesi artist and has contributed his marker styles to Piranesi users.

To use them, select the Brush tool then click on the down-arrow by the brush image at the top left to see the Style Selector. Change the category to "Wang Wang Markers" and click on a style.

Now paint your drawing. You can change the brush size using the options toolbar at the top, or by pressing the [ or ] keys.