Okay - I’ve had another play, and… 
… the airbrush setting works!!! 
There are limitations - the mask settings don’t include airbrush, so the cool edge effect can’t be utilised without moving the brush.
I’ve still managed some interesting dabs though - and it’s strangely hypnotic to watch the dab expand outwards from the tip… 
This is an example using the inbuilt tip creator -
edit: just realised @AhabGreybeard already said it works - sorry - I don’t seem to be paying enough attention! 