In Photoshop you can incrementally changed the size of the brush by clicking on a “bracket” key (please see Fig. 1 below for reference).
Clicking the “Left” bracket makes the brush smaller; clicking the “Right” bracket makes the brush larger - no modifier keys needed (Shift, Control, etc.). This allows You to keep working with your input device (in my case a mouse) on the image, changing brush sizes with the other hand on the keyboard without needing to go to a slider which is disruptive if one needs to change brush sizes frequently, which invariably will need to be done on a complicated mask.
The scroll wheel is a great idea - presuming one has such a capability. I think there should be a fallback short cut using the just the keyboard - a piece of equipment everyone will have.