The achievement pops as soon as you start
a match with four players: it's fine if you all quit straight afterwards
Therefore it's quite easy for a large number of people to get this in a single session. If you're reading this and still need the achievement, I suggest you set up a session for a month or two away and be clear that everyone who applies can get it, whether that's 4 or 5 or 20.
We got five people through in our session in about five minutes
EDIT: if you want to quickly make your own session, open this one, then select the menu (three dots), and 'Clone Session'Boosting Gaming Session for Worms