>>24736332What I do is have one of my teammates grab everything you want, go right up to before you exit which will initiate the Kecleon gangbang but don't leave yet. Have a ghost type Pokemon stationed near the stairs at least 2 spaces deep in a wall so the Kecleon don't swarm to the room with the stairs, but instead have your other two Pokemon stationed as far away from the stairs as possible having them set to "wait here" in the tactics menu, because that's who the Kecleon will be headed towards as long as your ghost is 2 spaces in the wall, including corners, giving your ghost type Pokemon an opportunity a clear path to the stairs.
Some things to consider are be sure to have a lot of food on hand, as waiting for an opportunity for a clear shot to the stairs could require waiting several turns, and staying in the wall eats up your hunger quickly. If you are willing to spend any orbs, is recommend a quick orb, as the Kecleon will be moving at 2x speed, so it will help even out once you make your path to the stairs.
The Kecleon will NOT stop spawning, so the earlier you can make a break for it the better since the map will eventually be overrun and your decoy party members will only last so long. They can and will sometimes spawn in the room with the stairs so be careful.
This method, while risky has been very successful for me, and is very cheap considering it can be done with no items, and at most use food, and 1 orb.