You will hear a sound when mixing mushrooms in your inventory. When you are wandering around, the same sound will indicated that a mushroom has appeared. You can also wait for the sound to play again to get another mushroom. Note: Listen for that sound when fighting the last Boss.
While fighting a Deadite or Hellbilly, turn on your chain saw and slash at them. After a few hits Ash will jam the chainsaw into them and keep it there. Then, use the ax and hit the Deadite while your chain saw is still in them. When they die, they will usually leave behind a Large med-kit. You can also use the other weapons instead of the ax, but it just wastes ammunition.
After receiving the note from the boys parents inside one of the tents in the Wolverine Troop's campground (the large one), you will see that the leader whom you fight later is named Mr. Nugent. After fighting the troop leader and reach Father Allard with all five Necronomicon pages, you will need to place something in the offering plate of a person named "Ted". Once you get the offering, you will see it says that it belonged to the troop leader. You now know that the leader is named after rock star Ted Nugent.
To avoid attacks and make your health kits last a bit longer while fighting the last Boss., walk up as close to the posts as possible after hitting them. Then, run a very, very tiny bit to the center of the ring towards the demon, then run back out. The demon will try to bite at you instead of blowing gas at you. Most times, he will bite and miss. Be careful, because after you do this a few times, he will move slightly towards the corner and be able to bite you right through the center of the post -- keep your distance while hitting that post.