I don't mean to be picky, but you should tell your partner to "Stay Put" or whatever it's called so that you don't have to wait as long for support. Plus, if it's NOT a monster house, you'll have to cross the room to wait for your partner to catch up after you change the tactic back.
All that said, you need to use either the bottleneck method, or use vacuum cut and discharge and possibly earthquake in conjunction (well, maybe not earthquake), or level up to 100 and wipe everyone out with a normal attack.