Simple make up applying question?

I know this may seem insane to do, but after you apply the foundation or any other cosmetic product lightly spray hairspray across the makeup. It does work, my boss does it for all my makeup when I'm called in for modeling campaigns. Either way, you shouldn't put on a "thick" or "heavy" coat of the hairspray because it'll make it too sticky and you'll have to wait a while for it to dry. Hope this trick helps!