The story's about bouncers hitting the hell out of customers are bullshit. I wouldn't want to work in a place were you have to charge on weekly basis.
The point of being a bouncer is as Vince stated, to let customers have a good time. That starts out at the door. Every bar has got his usual customers,
if you find out somebody is difficult to handle you don't let him in for a couple of weeks, if he's still difficult, you deny him the place at all. And not only at your bar, but at every bar in the neighberhood. That's not difficult to accomplish.
Once inside, make sure you have an emergencyroom and a chillout room. Sometimes customers tend to get very aggressive on a small thing like a drink on somebodies shirt. If you find out it's escaliting, take them both away from the scene make a talk, and after that it's usually okay. Sometimes the offender pays some money for cleaning or buys him a drink and that's it.
Once in a while, and I'm talking once a month or once every three weeks, something explodes and there is only one way to break up, and that's the hard way.
Break up, you take a couple of them to the chillout room, you send the other away after taking pictures and call the police and/or ambulance. But it ain't on weekly basis, and it shouldn't be. Going out is time to have fun, not to kick each others asses.
You're a proffesional bouncer, not a mma-fighter. Size helps, but making proper agreements with bouncers from other bars, waitressess and people at the bar so you won't have a mess.