I got to witness this first hand in GStar 2007. Also, here locally, I sometimes organize a “go-see” to check out models for an event.
I recently did this for the Level Up Babes. The LU babes were first seen at the POGS event. Since then, we get them for regular events and occasions. The valkyrie model, Joline, from the Valkyrie presscon is a member of the LU Babes.
Meanwhile, casting calls are not easy. Do check out the booth babe girl search for Bloodrayne on E3.