Coconut oil can be applied to both wet and dry hair. However, as a general rule, it should mostly be applied only to wet hair, as that is when the hair will be able to properly absorb it, and when the coconut oil will actually prove to be beneficial.
If too much coconut oil is applied to dry hair, instead of being beneficial it might just cause blockage, or buildup, which then leads to negative consequences.
So we recommend sticking to wet hair when you are applying coconut oil hair treatments, and if you are going to use some on dry hair, make sure it is a very small amount and do not apply it too often.