In terms of intensity, few events rival the scene backstage at a runway show. The space is tight, but with shows scheduled on the hour (and many coveted models walking for multiple designers), the turnaround times are even tighter. So when, for example, a six-foot-tall brunette dashes in five minutes before showtime with platinum-bleached brows, shellacked hair, and puffy eyes from an allergic reaction to the last makeup artist’s lash glue, these pros need every quick-fix trick in their bags. Here, the masters divulge products that produce backstage heroics.