So, even as an anti-aging obsessed skin-cancer prevention advocate, I have to be honest: reapplying sunscreen is the pits. Maybe you have makeup on... maybe your hands aren't clean and there isn't a sink nearby... maybe you just don't feel like slathering goop all over the place! Here's a nice solution to the re-application challenge: Sunscreen powder. If you haven't tried one of these, it's worth a go. Mostly all of them are appropriate for anyone 6 months of age and over, and they are NOT MAKEUP. This means you can put it over your existing makeup, or apply it to an unsuspecting husband, boyfriend, or son.
Here's a link to my favorite one so far, Colorescince Sunforgettable: http://jxeqr.jklky.servertrust.com/product_p/brush50.htm
I would personally get the medium, (I am a somewhat fair caucasian) because the light is pretty darn light and the darkest one can start to look really dark and almost muddy on light or medium skin if you reapply more than once (the whole reason we are using sunscreen powder, right? ...to re-apply!!!)
If you don't already own a spray brush cleaner, I would probably get one so you can clean the brush in between uses. GloMinerals is my favorite, who's brush cleaner actually smells AMAZING (almost like strawberries, but better!) and dries a little faster than some: http://www.gloprofessional.com/brush-cleaner
Now get out there and re-apply!! :)