Rounds 1-5: There are 4 windows, and 4 people so obviously everyone gets their own window. I advise Knifing the first 2 rounds to maximize money possibilities. After the first 5 rounds leave up stairs, try to get a crawler before you leave. Once you buy the upstairs door, take a right and go towards the power room.

Rounds 5-10: Turn the power on, and make sure not to open the far gate door to the downward staircase. Everyone use the box and 2 people with the best guns, such as Lmg's get the staircase, while the other 2 get upstairs with the box and window. You can maintain this until 10.

Rounds 10-30: Just follow Gawleys strategy for the rest. I find this too work the best. And he has a great video to demonstrate it.
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But Yeah its pretty easy to follow, and mostly common sense. Atleast I found it to be.
+ Rep if this helped. Thanks
Add me if you would ever like to play gt: Cpt Bushie