The new sand blaster is functioning well enough for use, though it still needs a few tweaks.
To turn the air on for it, flip this yellow half-turn switch leading to a green hose right between the air compressor and the garage door. (The position shown is off.)
The master power switch on this panel underneath turns on all the lights and the vacuum cleaner. (The vacuum cleaner must be on to use the blaster.)
The tweaks remaining: putting a local air switch on, plus a pressure regulator. Repositioning the vacuum system out of the way. We’ll be getting the old blaster’s foot petal back soon. And while I polished part of the window enough to see through — it was practically opaque! — the whole window should be done at some point.
I suspect the latter will be a periodic maintenance task. If you use the blaster regularly and want to help out, it’s very easy to learn how to do this.