Once you decide you might want to use sun screen, try several brands to find out which are the most tolerable. Neutrogena (70+ SPF) and Banana Boat (100) are a couple I'm familiar with. The Neutrogena goes on dry-feeling, with minimal ick factor; the Banana Boat is a bit thicker, as I recall, harder to spread, but may stay on longer, and is also not greasy feeling.
There is on the drawing boards a sun screen with SPF of 873. Put it on, and massive dark clouds completely blot out the sun, so, needless to say, agricultural interests are fighting its deployment.