We had a dog come into the grooming salon with cutaneous horns and massive sebaceous cysts all over his body. I'd always volunteer to clean him because the groomer was afraid to touch them, but the dog just seemed so much more relaxed if all the horns happend to pop out of their pores in the bath, and the cysts were emptied as much as they could be and cleaned well.
The first time I did it, it was an accident, I bumped a few of the horns off as I was helping the groomer with bathing some of his dogs, and he mentioned that the dog was much calmer. I started volunteering to wash him and made sure to knock off what I easily could (wasn't forcing anything, just what I could gently brush off with my fingers) and clear out what I could. Another groomer saw me doing it once, had to leave because she said it was too gross.
Though that was far from the worst thing at that store. There was the contstant emptying of anal glands, which at least once resulted in anal gland juice in someone's mouth. (That'll teach you to talk while working on bottoms!) There was also the dog who was terrified, groomer unhooked him from the drying table because he was about to choke himself, he ran up front and hid on top of the printer in an alcove, spewing poop the entire way. We had to get a new printer after that, and the groomer had to clean up the floor on her own. (She had disregarded repeated written and verbal instructions on how to keep this dog from freaking out like it did. She caused the mess, she had to clean it up.)