We have a desensitizing spray called Stud 100. It primary purpose is for premature ejaculation and does so by numbing the penis. It also does it rather effectively and it’s a really strange sensation having little or no feeling down there. The best I can describe it as is how your mouth feels when the dentist gives you an injection.
For its intended use a small amount is sprayed, just enough to prolong sex and keep you partner happy for longer. Too much and you lose all feeling and can even , according to the product literature, cause your erection to subside and make you lose the urge.
So what could a devious Key Mistress do with a good dosage that’s guaranteed to numb? Control your erections, allow masturbation even intercourse happy in the knowledge that there will be no orgasm. And that is definitely orgasm control and denial.