To make this simple. Just purchase 1-2 quarts of 3% hydrogen peroxide and add to the other bath ingredients in a hot bathtub of water. Unless you are a purist, there is no need to purchase food grade H202 for your bath.
Use 3% for spraying on skin after showers.
Moreless does suggest spraying 3% into one's mouth and then inhaling to help alkalize the mouth area and get more oxygen to the lungs. The way I do it so as to not spray too much or let big droplets go into my lungs....I just open my mouth and spray under my tongue and inhale as I do it. The finer particles of H202 make there way to my lungs. If one was to spray directly down their throat, there could possibly be a big reaction between the acids there and the oxygen, which will cause one to cough quite a bit....you know how H202 bubbles up.
The use of food grade 35% or any other high percentage H202 has more cautions than I care to get into. A person should use common sense and not be distracted while doing the math to figure how to mix 35% to 3% or while mixing/pouring it.