I frequently use MSPaint when brainstorming or deriving equations, and had become quite proficient at handwriting using the mouse. I reduce the mouse speed whenever I need to make small-ish annotations without zooming in, then switch back to normal settings for interacting with GUI.

Many fancy mice have "on-the-fly" adjustments shortcuts that only works with their proprietary driver, and only for their specific devices. If I'm at a workstation with a generic office mouse then it's very cumbersome to constantly go back and forth between Control Panel and the application when switching between drawing and navigation.

So I wrote this little "Volume Control"-esq tray app to make it so that I could just hold down CapsLock and move the scrollwheel to adjust the mouse speed, and click the middle button to reset when I'm done.