Unlike haircuts, massages, facials and manicures -- beauty treatments too subjective even for this annual benediction -- an eyebrow wax is a pretty straightforward process. A few yanks of the wax-lined cloth strip, a few follow-up pulls of the tweezer and voilà: Either you wind up looking like a surprised Joan Crawford or you emerge with a pair of refined, elegant brows, the kind that will make your friends say in the days to follow, "You look great! Did you do something different to, like, your hair? Are you wearing makeup?" Such a utilitarian ablution shouldn't cost you twenty bucks, as it often does at hoity-toity spas around town. Which explains why the wax job at Nail Studio, located in a blink-and-you-miss-it shopping plaza on Delmar just east of Union, is the place for you. They'll sit you down in an office chair, have you lean back, ask how much arch you want...and five minutes later you're on your way, looking lovely, feeling fine and only seven smackers the poorer for it.