Prepare oatmeal per instructions. Use plain or add other great skin care ingredients like ground almonds (which also mildly exfoliate), clay (kaolin is suitable for all skin types), or essential oils (add only a drop of non-irritating essential oils. Essential oils good for most skin types include lavender, chamomile, palmarosa, or geranium). Add extra liquids (like honey, etc) if needed. Apply to damp skin, leave on for 5 to 20 minutes (5 minutes if your skin is extremely sensitive; 15-20 minutes for most other people). Rinse well.
After cleansing or masking, be sure to tone/hydrate and also moisturize the skin Oatmeal cleanser or mask technically don’t need a toner after use, but I still recommend using a natural toner to hydrate the skin.