After you get the Fly Honey, you can get something that will help you end the zombie apocalype.
Get the Zombie Paper
Now that you have the Fly Honey, wander around until you get a call from Apple Kid. He tells you about Zombie Paper. Wander around some more until the Mach Pizza delivery guy appears. He gives you the Zombie Paper.
Use the Zombie Paper in the Tent and Stay at the Hotel
Go into the town's central tent and use the zombie paper there. Then spend the night in the hotel. The zombies will be lured into the tent overnight.
Use the Graveyard Secret Passage
The next day, you can go see the zombies in the tent if you want. Otherwise, make sure that you have the Jar of Fly Honey, and get good equipment for everybody, and buy some healing items if you need them. Then go to the northwest graveyard and go to the northwest corner, then go northeast to find the entrance to the secret passage. Go down the ladder.
The path is straightforward. The first large room contains a Skip Sandwich DX, and the second large room contains a Silver Bracelet. If you get possessed with a mini-ghost, just ignore it. You can cure it soon.
Go east until you find Mini-Barf. During the battle, Mini-Barf will exhale a blast of stinky breath, which makes all members of your party start crying, which reduces your accuracy. However, this only affects accuracy of physical attacks, so use PSI attacks if you are crying. If you aren't crying, use physical attacks to conserve PP. You can use Healing β or a Cup of Lifenoodles, Horn of Life, Secret Herb, or Refreshing Herb to cure the crying, but Mini-Barf will exhale stinky breath again, so curing the crying might be a waste of teim.
Have Jeff heal Ness and Paula if necessary. If Jeff has Bottle Rockets, or if anyone has bombs, use them to deal a lot of damage.
After Mini-Barf is gone, go up the ladder to reach the Grapefruit Falls area.