Not only will this keep your skin hydrated, it will also act as a barrier between your face and your mask, reducing friction. Apply onto a cleansed face before and after wearing a mask.
Look for moisturizers that contain ceramides, hyaluronic acid, or dimethicone, which will provide extra protection. Take care to avoid fragrances amongst other common contact allergens. This may take trial and error to find the right formulation for your skin type.