Do the following to have an infinite First Aid Spray, Green Herb, Mixed Herb, or any healing item you wish. First, make sure you DO NOT read the Instructions Book file that you get at the beginning of the game. Get any gun (except the knife) and get the healing item you want for the glitch. Make sure that your inventory is organized in the following order:
Your Healing item.
Equip your gun and then read the Manual. READ IT FROM THE FILES SCREEN. DO NOT CHECK IT. If done correctly, you will have your healing item equipped. If that's the case, exit the inventory screen and fire your gun. Now use your healing item. It shouldn't disappear, it doesn't matter how much times you use it. It will still work if you store it, so Chris should be able to use it, too. DO NOT MIX YOUR HEALING ITEM. IT WILL LOSE HIS INFINITE PROPERTY. This should make getting the Rocket Laucher a piece of cake.