I'm sure you would get enough interest in doing it as a SIG, but there would be some major considerations to take in mind. Mostly, all of the SIG rooms are carpeted, so you would have to bring protective covers (tarps, sheets, etc.), so as not to damage the room. As for how "naked" you could get for the painting, I know it's stated in the terms and agreements of the con. But, roughly, a t-shirt, shorts, and sandals would be a bare minimum (no exposed private parts, male or female) when walking around the hotel, but in the SIG itself, you could probably get away with just shorts as long as no one objected, assuming the person being painted was male.
As for walking around the hotel, it's mostly common sense that would have to be used. No damaging the chairs, tables, or carpet of the hotel with the paint, regardless of how easy it is suppose to be to wash off. Also, there is the major concern of damaging other's fursuits. I know furs have used bodypaint in public areas during previous cons.