A good way to deal with large hordes?

I pulled into rosewood and there were a LOT of zombies. I made my way to Gigamart and was able to loot some of the shelves but not all and I was running out of storage. I went to back to base and unload my stuff and went back to rosewood. When I got there, there were even MORE zombies that just popped up out of nowhere. Any way to deal with a large horde?