This quick and easy key combinations allows you to make adjustment in 1/4 blocks of the scale to fully dial in your levels, and it works for Volume and Brightness.

Volume

Volume Down - Shift ⇧ - Option ⌥ - F11

Volume Up - Shift ⇧ - Option ⌥ - F12

Display Brightness

Brightness Down - Shift ⇧ - Option ⌥ - F1

Brightness Up - Shift ⇧ - Option ⌥ - F2