Play on a map like Avalanche.

Go to the one side of the map where you can climb up onto the rooftops of the stores from the two sets of stairs.

Wait til about wave 7 or 8.

When the maulers come (shield carrying locust) kill them and take their shields.

Set the shield up BACKWARDS in front of the staircase. Set it up so if you were walking down the stairs, the "kick shield down" with the X-button appears. Set up in front of both staircases. the way listed above.

Now no locusts come up the stairs.

At the end of each wave, the shields must be retrieved or they will vanish.

By repeating this step each wave, the horde mode should be beaten much quicker.