We did the same to a guy nicknamed “Tex”. We used GI brushes and Pinesol concentrate right out of the gallon bottle. After that Tex was the cleanest, most strek troop you’d ever meet. Might seem cruel but that old boy wouldn’t shower and we lost three weekend passes in a row. He survived the scrubbing, though a might sore. He turned out OK.
LOL...Everyone had a guy named “Tex”...he was from Brooklyn!
Seriously, as you said, some people might think it was cruel, but there were cases you had to do that kind of thing.
We had a guy in my squadron who was nicknamed “Stinky”. He was a BIG guy who reminded you a bit of Mr. Incredible with his body type (enormous torso, neck and shoulders, and little-bitty legs) and was a very nice and friendly guy. But he had hygiene issues.
More than once I heard him growl at someone menacingly “Don’t call me Stinky!” and it occurred to me that if he hadn’t been such a good natured guy...they wouldn’t have called him “Stinky” to his face.