If both parties have the the same app, or an app's that can talk to each other (e.g. can read QR codes) then sending a QR code to one anther is easy. Otherwise,

If both parties have the the same app, or an app's that can talk to each other (e.g. can read QR codes) then sending a QR code to one anther is easy. Otherwise, in real life, even writing down the email of just another guy is a pain.