the guide is a bit flawed for a charm play endurance/mind build is way superiorI actually wasn't descriptive enough when I mentioned a Charm build, so I'll add more detail to that. But first, I mentioned sub-10 slut level is doable for a Fighter. I think while building Charm, sub-20 slut level -might- be doable on Prisoner difficulty to get the +2 Charm reward from the boss, but you would have to rush it before passives start stacking up. Have only done it on the easier difficulties myself.
So a bit more explanation on building Charm. Keeping desires low and playing passive (spamming Cautious Stance) is a means to level Charm. So yes, this would be the prisoners literally just jerking themselves senseless in your presence. However, once you reach level cap, gameplay would transition into something else of your choosing.
Having high Charm and unlocking Flaunt, enemies will mostly be trying to take Karryn's clothes off, or jerking themselves as opposed to using regular melee attacks. If you wanted to start playing as a Fighter from here, you could see this as a form of crowd control. You would also have access to more equipment, giving you a nice power boost there. You could also transition into being slutty, but you would have to equip the accessories you want before you start stacking passives, because you will probably lose an equipment slot (0.1 charm lost per slut level gained). The main difference between a Charm built slutty Karryn and an Energy built one, would be the control you have over the prisoners. Ideally Charm Karryn is in control of a situation and generally keeps her Stamina above 0, while Energy Karryn is usually always on 0 Stamina, but will never get knocked out because she can't cum fast enough to lose all her energy.
Using the handjob skill only requires cock desire. So, you could keep your slut level somewhat low if you get the handjob skill, then keep all desires except cock desire low. Then just give everyone handjobs. There's a few skills under the Mind tree called See No Evil, Hear No Evil, and Speak No Evil (reduces all desires). Having the set-bonus from having one of each accessory equipped also reduces the cost of skills (Willpower skills included), making the use of Speak No Evil much easier. So giving everyone handjobs while keeping desires low is actually possible.
Hopefully this clarifies things.
Edit: Apparently Speak No Evil does not work in the current build, so don't waste your time getting it.
why?
you have to let them strip you first to charm start to work aside from guards