The Whipping Boys are a Legacy that uses BDSM techniques to achieve a trance state, pushing themselves beyond pain to find enlightenment. Of course, that involves moving past the initial feelings of disgust or discomfort, or even homophobia, experienced by the mage.
The Whipping Boys are entrenched in the Sleeper S&M culture, and as such ride close to some seedier practices. Given that, other, more conservative mages tend to regard them as freaks or perverts. But the Whipping Boys, beneath their hedonistic ways, have a deeply spiritual side, and roots in ecstatic traditions the world over. They believe that through extreme suffering and sensation, a person can reach a place in which the soul is unfettered, unconstrained by any part of the body. The consciousness can then be reshaped, so it's important to enter into the experience with a clear goal.
Most of the time, the Whipping Boys use the practice as a way to focus and refine their use of the Dream Merit, but the "Session," as it's called in the Legacy, is also the method by which members advance. In addition, the Whipping Boys claim that a Sleeper who undergoes the Session and remains conscious can reach the Supernal Realms and Awaken. "Session" is the rather euphemistic title the Legacy uses for its hours-long ordeals of sensory overload. Although pain is a large part of it, Whipping Boys also use pleasurable stimulus (though never actual sex) to bring the supplicant into the desired state. Different members of the Legacy employ different methods -- electricity, fire, cutting, whipping, pin-pricks, and extremes of cold and heat are all possibilities. The mages aren't above using magic to achieve effects that no Sleeper master could hope for, and, likewise, the Whipping Boys generally keeps a healing spell ready (hung using Time magic, if possible) in case things get too far out of hand.