So first, this is a non-risk activity.
Herpes doesn't infect the breast area. The skin there is too thick to infect. I suppose if the skin was broken, it could, but if someone was infected in a non-mucous membrane area, they wouldn't be shedding the virus from that thicker, intact skin later. Without an outbreak, they would be non-infectious.
Obviously, it's a good idea all around to not rub your genitals anywhere someone has broken skin, no matter the cause of it.
The strains of HPV that are sexually transmitted also don't affect other areas of the body. They affect the genitals, the anus and the mouth. That's it.
"Minimum level of cleanliness"? I'm not sure what you mean here. Do you mean the person? The setting? I would expect that all people who have multiple partners in a short period of time - paid or unpaid - would shower in between partners, or somehow otherwise clean up. If there are towels on a table, I'd expect the towels are changed in between clients.
You assume that CSWs are most assuredly carriers of herpes and HPV. I need to correct a couple of things here. First, there is no such thing as a carrier of herpes. You have it, or you don't. If you have it, you are infectious from the site of your infection. CSWs may have slightly higher rates of infection than the general population, but they aren't walking STDs. They are usually insistent on taking precautions. It's not to protect you, but to protect themselves from you and their other clients. Their livelihood (and their lives) depends on it.
Also, most people who are sexually active have, have had, or will have, HPV. It's considered an inevitability of sex now. Some experts say 90% will get at least one strain at least once in their lives, other experts say everyone. (The only people exempt from this are those who have only had sex with one partner, who in turn has never had any other partners, ever.)
You can assume that anyone you have sex with has HPV, and you probably wouldn't be wrong. Several strains don't give symptoms, so you'd never know you have it.
So to recap - no risk for the boob job, and CSWs are just like everyone else - assume there is a risk with everyone, and act accordingly.