#1 get the Hill Billy out of the jail and get Candy
#2 kill zombies till one of them drops a power up
#3 Give Leroy/ the Hill Billy the candy next to the power up
#4 Wait till he starts doing his thang on the power up and shoot him while he is trying to change it into another power up
#5 kill more Zombies to get more power ups and give Leroy more candy to make more permanent power ups
Hope you enjoyed, follow me so that i can make more posts and provide some more zombie packed tutorials, tips, and tricks
P.S. Doing this trick and keeping the power ups for high rounds HELPS A LOT!!!