What's the noun for backslapping? Here's the word you're looking for.
backslapper
One who makes a show of liking another person with profuse or excessive displays of camaraderie, such as vigorous hand clasping, back-slapping, hearty words of greeting, etc.
“As a former international with 108 caps, he has taken steps to shield his players from DFB officials, sponsors and other backslappers, especially during team meals.”
“Not donating to egotistical backslappers Jeremy Jones ALL this looks like to me is a bunch of millionaires trying to promote their careers.”
“Calderwood, for one, was nowhere to be seen in the queue of backslappers waiting to salute the Blackburn striker's century of Premiership goals.”