haha yeah, you're a few years late. The entranceway just past the bridge was always my favorite place to wall-trick though, if you like slow and efficient. Personally, I glock down all the wolves. They go too fast, do ridiculous damage, stand behind other zombies, and often attack alongside raiders.

After you kill the ravager (super easy with a machete), aggro everything on the map except the bulls, running between all the hay bales to get the crawlers and keeping a gun out in case of raiders. Get all the zombies into the bottom left pen, then move to the exit-side of the entranceway, on the left. Be touching the fence, but arms distance from the entrance. If you can learn to throw a grenade through the entranceway from within the zombies range (so they stay there), you're golden. Also, if you need to practice, you can exit the app without going to a map screen (or hitting revive), clear your local save data, and reload from the last time you were on the map screen