Basically what you'll need for pumpkin boss are the following

Stick Matt | Stedro | Ben Stickobi | Marcstick | Stick wes

The ideal strat is to spam wes during the shielded part and use your combo with andrew to get some nice damage, you can also use the others but you need to get really lucky so the boss doesnt hit them or they dont get hit from the zombies. after he loses his shield, spam everyone and use andrew's FC to get really nice amounts of damage, you can get him dead in no time.