If I wanted some tips on how to shotgun a beer like Luke Combs, I'd ask Luke Combs. Y'know, if we were friends. Ed Sheeran is a friend, and he was kind enough to post a video of the lesson he got from the man.
Luke gives him the basics of how to hold the can correctly and what to expect when the beer starts flowing. Then they do the shotgun and Luke finishes in about three seconds. It takes Ed a bit longer.