After I'd grown a beard and gone to an RC, I noticed a few people who were friendly to me by their facial expression. One young bro was an attendant 'guarding' some door during the sessions. Obviously he was freed from listening to the program. As I walked around taking a break from the talks, he made a point of smiling at me. Most people who saw me made a point of not looking at me directly. I suspect he was probably PIMO.
So you could find some man with a beard and discreetly follow him around, watching for the few who smiled at him. Then you could drop a line to them like, 'I need a break from the talks. How do you like this guarding job?'