Don't tell anyone but half the high-end upholstery we do we just shampoo as well..
Nobody ever sits on this crap, It's just a little dingy from dust and HVAC below back and a couple of flea spots...
“Flood and Flush” isn’t needed, nor is it a good idea, for fabrics as thick as your shirt sleeve.
I can’t remember the last time someone called me with a damage claim that resulted from hand cleaning, other than texture damage to velvet or chenille.
Just don’t sell protector....rarely works as well if you don’t rinse.