Run through the mission like you normally would up until the part when Buck goes down and the walkers are over him. DO NOT shoot your weapon or even go over and mele them. Simply allow the walkers to down you and then watch the cut scene. As Daryl simply follow the on screen cues to progress in the mission. When Jesse tells you to go out the back there will be a walker blocking your path. In order to get by without killing it press the to shove the walker out of the way. This is a great technique for the entirity of the mission in case walkers get in the way of your fuel targets. Simply collect the 3 fuel cans and make a beeline for the truck.