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There is not one agreed upon oil for the inversion method. Try olive oil, castor oil, coconut oil, grape seed oil, or Moroccan argon oil, if you want to use natural ingredients. Choose an oil with an aroma that you find soothing. Since the inversion method incorporates massage, pick a scented oil that you find relaxing. Warm up around 3–4 tablespoon (44–59 ml) oil. Take a cup of hot water  and place your oil bottle in it. You can get this water from the sink. Let the oil sit for a minute or so until it is warm to the touch. Your goal is to increase blood flow to your scalp. Warmer oil will increase the blood retention in your scalp cells. Do not overheat the oil. You don’t want to burn your scalp. If you’ve experienced hair loss, make sure that you cover your problem areas first, then proceed to cover the remainder of your scalp. Make sure that you cover your entire scalp with a thin layer of oil. It doesn't take a lot of oil to achieve full coverage. If your hair tends to split or break, try to spread oil to all of your hair. Hair splits or breaks when it is short on moisture and nutrients. Natural oils will help replenish both. If you have curly hair, be gentle or avoid this step altogether. You don’t want to pull out more hair in the process.

Summary:
Choose your oil. Warm up oil. Apply oil to your scalp. Comb the oil through the rest of your hair.