That's one I've never heard of. Learn something every day! Poor fella, that had to be a bit uncomfortable.
I'm with usandpets, make sure the hair got out. Before I type this, I will say I'm not a fan of sedatives to overrule training, but in this case if it was one of mine and he wasn't comfortable with it, I'd get a tube of Demorsedan gel and get him cleaned really good while he was a bit dopey just to be sure the hair was out and then go back to desensitizing him there. That would give you time before he needed cleaned again to work through it.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.