No nails & no mobile phones or cameras, most of us would like to keep our privacy.
An outdoor & isolated location would be good, nothing like feeling the cool wind on one's bare skin or else the hot sun.
A mixed group essential, equal numbers of males & females, that would keep it safe.
Victims to dictate the severity of the ordeal & what they want is respected.
Keep to rules of safety & privacy & it could be a regular event. If it works it could be a model to be repeated in other places in the world.