blindfolded "guess who" mid-play, anyone do this w multiple couples?

so weve been to a few privates in toronto where the host does a "blindfold guess who" round, basically one partner is blindfolded and has to guess which of the other partners is interacting with them... could be their own partner, could be someone else, no obligation either way. its way more fun than i expected, the not knowing is the whole point. question is how do u set rules so its safe and consensual every step? we're thinking of hosting our own version and want to do it right... e.g. how do u handle when someone wants to stop, do u use a signal etc...