Start: If you have butters or kenny in your hands, throw it in the middle. If you don't have them, play cartman behind your new kid. 3rd option is play wendy behind your new kid so she can charge up then put a heidi/nelly in front of her to tank hits.
Mid: Just counter play them with your zen cartman and always use cartman's ability to change aggro. Don't let them kill your wendy. Always make a good value damage using your wendy ability(make sure you hit 2-3 units especially the assassins since you can 1 hit them when your wendy is level 2).
End: If you're winning a 3-4 unit push, use regen.