Your Dendera sandblasters are from the Ptolemaic period.
If you didn't know, that makes them Greek and well within written history (in fact, they are utterly explained right there on the walls in the same rooms containing the artwork.)
So, the Greeks had sandblasters. Then the Romans must have had sandblasters too.
But you don't wonder why they never wrote about them?
I own a large, in line sandblasting unit. It requires a large rotary 3 Phase air compressor and a tank which is approx. 10 ft. tall. The motor is 50 hp. The unit needs to reach 80 bar. cfm (cubic feet per minute). Require my forklift to even move it.
Please tell me, what powered your sandblaster from the Dendera or Ptolemic period.
Additionally, my equipment is loud, and requires a cyclone cleaner and an air dryer. It is nearly impossible to keep fine dust from escaping, which then enters into your other equipment, and damages them. We have to run this beast every week or so. I hate it. Even with all of this pressure, it would never be able to cut through rock.
Maybe the AE had a water jet too?