And Keyboard Maestro can drag the mouse. […]
Whether any of this works with Photoshop is anyone's guess.
The dragging action works fine here with Photoshop CS6. 20 mouse pixels increase the brush size by about 46px.
@dream3 I just tried the original macro in Photoshop and with dragging the mouse (manually). It works, but after hitting "T" you have to wait for ~0.5s before starting to drag.