Pfffft, you believe stuff that is in the readers digest? That article is a bit of bull IMHO.
Talking to a doctor and they said all you need is 5 minutes a day on the area of skin the size of the back of your hand.

The real concern with this issue is that some people, such as those in nursing homes don't get to go outside at all.

If you are still concerned, at least put sunscreen on your face and neck, the parts that get sun pretty much any time you are outside. If you at other figures it only takes 15 to 20 mins a day on unprotected skin to get skin cancer. Coming from the melanoma capital of the world, it's something I'm a bit opinionated about.

As for sweating, decent sunscreens don't sweat off. Where do you think the waterproof ones come from. The idea is you apply it at least 10 minutes before you go out into the sun so it soaks into your skin. That way it doesn't come off. So if you are commuting to work for example, just apply it before you have breakfast of something.