Does the "waves" answer work with OP's question of "how to do it without taking a long time to run?"Waves, like others have said.
But also more set pieces (walls with a batista, catapults, lightning rods), time constraints (they will escape in 2 turns, the room is flooding, enemies get resurrected every other turn), in addition to the monsters.
Give the monk a reason to dash up wall, or a wizard to cast pass wall, or a Barbarian to roll Athletics.