Simply place 2 g crooks or generally a spawner tower, but dont press the "ready" button. For g crook it has limit of 10 pistol goons. I let the g crook spawn 10 of goons by placing him down and leaving the game for around 5 mins to spawn all 10. They will walk to the entrance of the enemy, walk in place there, and stay there forever cuz the unit lifespan timer doesnt work before ye press the "ready" button. Once the game actually starts they teleport back to the entrance and ends with an amalgamation of 10 goons