Have you tried these?

[Becky]

I have the Specialized ones, and really like them. They're featherweight and, while they're not cooling (unless soaked with water- ahhhh!), they're not hotter than going without.

[marni]

I love my desoto arm thingies. Here in Houston they are good as a light arm warmer on cooler spring, summer, and fall days and as arm coolers the rest of the time. I often wear them under a waterproof jacket when it is extra cold. It's usually all I need unless the temps are below freezeing. Of course in Houston..... They definitely prevent the sting of the sun, let the air in, and it find it more comfortable without wet slimey arms.

+1 on putting on the sunscreen an hour ahead of time, letting it soak in and then adding another layer just as you go out the door.

I have redish auburn hair and green eyes so the absolute first question I always get from any doctor is "You do wear screen all the time don't you?"

However you can keep the sun off is a good thing.