Adjusting Flow in Photoshop. Why and what do you use it for?

I never really touch the flow command. Am I missing out on a powerful tool in sketching/rendering?

This video may help explain the basic principles of opacity/flow if you do not totally understand how they work. I am sure other users here can explain or find a better video.

This Scott Robertson tutorial also briefly goes into how he uses flow/opacity

Also, it seems that to better utilize flow/opacity it would be nice to use a drawing tablet or cintiq style drawing tool due to the use of pressure sensitivity.

I think the basic idea with flow/opacity is that like in real sketching/marker rendering, you can build upon markings to add more highlights/depth or potentially add gradients that may create illusions of curves or certain materials better than without it.

Excellent, thanks! In that Scott Robertson vid, I notice he uses a hard edge brush in a triangle shape. Never seen that before. Looks like I need to invest more time using the pressure sensitivity function on my bamboo.