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You don't need anyone to help you with that, i did it solo

It's quite simple. Just kite around the map, until a normal hillbilly-clot is in front of a Husk and kill him with a headshot. I think it's even easier with the M99, but since that weapon is a bit more expensive, you'll have to play more rounds.
I would suggest a solo game.

Solo. Beginner. 'Nuff said.

You don't need help, it is easier on Mountainpass, though

play solo on beginner/normal
last round buy crossbow and kill the Husk while other zombies in the line