Opacity, Flow and Mode
The opacity of the brush tool can be quickly tweaked using the number
keys: 3 = 30%; 3 + 5 = 35%; 0 + 3 = 3%; 0 = 100%. Holding Shift when
inputting the numbers sets the flow of the tool. Note that if Airbrush mode
is on, these two shortcuts swap (i.e. holding Shift controls opacity instead of
flow). You can toggle Airbrush mode on and off using Option + Shift + P.
The same numeric input method can be used to determine the opacity of a