NHS Podiatrist:
"Did you want to do this"? Nope , I was plied with cheap voddy and press-ganged , woke up on a boat, let off when I was qualified
"I couldn't do your job , messing about with people's feet" I don't mess about thanks, and we wear PPE (Personal Protective Equipment) . There are jobs where they put their gloved hands in far worse places
"D'you need to study to do this" Uh huh
"Do you use a fresh set of instruments for each person" Of course. And gloves,apron,paper on the couch
"Do you have to deal with people with dirty feet." Occasionally. But more the blighters with BO. I can refuse to treat dirty feet for safety reasons. Can't send someone home to blast the RightGuard
"I better watch you might cut my toe off. HaHaHaHaHa" Believe me if I thought I could get away with it , I'd aim for the jugular Tinkly little laugh.
Obviously all these are only replies in my head. I am Pro....Fessional 
And on the rare occasions I have an empty waiting room and I can have a drink and a pee "Oh you're not very busy....."