Any oil that is considered as suitable for the scalp in our Ultimate Guide to Hair Oils will normally be beneficial to a dry scalp (except personal sensitivities). Each oil will have different properties and benefits that can help in specific cases like hair loss or irritation. But in general, if the oil is not considered as comedogenic or irritant for the skin (aka suitable for the scalp) it will be a beneficial ingredient to keep your dry scalp nourished. As a general guideline, you can apply your oil mask on your scalp and massage for a few minutes then let it rest for around 30min before your shampoo. Make sure to also consider humectant ingredients which are also key to help a dry scalp to heal.