You can find more about the Battle Maison in the proper subforum.
But the standard Entrainment team is:
Whimsicott
Durant
Mega Gyarados (Waterfall, DD, Protect, Sub)
The idea is that Whimsicott abuses Prankster and Focus Sash to cripple the enemy's lead with something like Stun Spore and Memento (Taunt, Encore, and Switcheroo are also popular choices). Then Durant comes in with Choice Scarf to transfer the ability Truant to the enemy with Entrainment. Then Mega Gyarados comes in to set up to +6 with DD (setting up both Atk and Spd is crucial). Use Protect every other turn when the enemy has an attacking turn and use Sub to avoid damage from priority or status moves. Mega Gyarados is the preferred sweeper because of Mold Breaker. There is only room for one attack on the move set, so it has to be a type which no pokemon is immune to and which itself has few resistances. (Water otherwise does not satisfy these conditions, but Mold Breaker allows you to bypass Water Absorb.)
There are some issues to be aware of and some situations which can screw you over. But the strategy is pretty much foolproof. Battles take forever though, even with battle effects turned off. I saw someone used Drapion in place of Mega Gyarados (Protect, Sub, Acupressure, Knock Off). In general, the team must be
Prankster Crippler
Truant Entrainment Durant
Strong mono-type setup sweeper (which can get both Atk and Spd boosts)
If you are just looking to get a streak of 200, I will tell you that I did it rather easily in Doubles with the following team:
Yache Berry Garchomp
Focus Sash Gengar
AV Azumarill
Mega Scizor
(I also easily got 200+ in Triples with a Trick Room team, anchored by Mega Abomasnow. But Triples battles take so much longer to complete. Each battle is like 4 or 5 minutes even with battle effects off.)
You should take a look at this thread:
http://www.smogon.com/forums/threads/battle-maison-discussion-records.3492706/
There are a lot of good examples of BM teams and good discussion about team building for BM.