Seriously, this is so broken that it should be balanced out somehow.
You just have to get an empty shopping cart and drag it everywhere you go. As long as you can keep the cart between the enemies and you, they will enter the cart first with a 400 movement cost. More than enough time to attack it once or even twice and move backwards, dragging the cart with you and making the enemy spend another 400 movement.
Hack, step backwards, repeat.
You can even remove the box and leave only the casters to make the obstacle ultra light, removing any movement penalty for dragging a vehicle.
With this method, I am even able to kill Zombie brutes with a starting character and a starting weapon. And because that, this makes the game a lot more easy, at least in the beginning, as long as you can find a cart.