Okey, just a more easy and quickly solution....
in the storehouse (where you start as Foxy and Mike is next to you)
go with mike, then just hit some boxes until you get enough material to make a bomb and put it in the middle window (wait a few minutes to have enough zombies around, then just keep the other two barricades OK, (so they can't get in, and when the bomb explode this one will take the 3 windows spots)
and 10 easy points...
Thanks to Zedarboy for making the video...