I got to the point where I carry an old thin long sleeve shirt when I travel.
If the sun is on the drivers side I just pull on the left sleeve. Cooler than the sun beating down on your arm.
If I am in a convertible with the top down, I put it on both arms of course.
Saved me a few nasty sun burns over time. The new sunscreens are better though. The old ones would turn your arm green and that was REALLY funny looking