Specularity implies a direct reflection from the light source back to the camera (eye) where you are seeing the source itself. So the first thing that needs to happen is you need something to reflect, light sources in VW are infinitely small and will not cast a reflection. Area lights do in other programs, I can't remember if they do in VW. But you basically need something like an HDR background of what the lighting plot is, so that the reflective bits can pick them up at various angles. Your spots of glitter paint are all reflective, but the actual surface is very bumpy and so therefore "glitters" as light comes from different angles to either be seen by your eye or not. This effect is much more apparent when your camera/eye moves, picking up different specular highlights due to the changing angle of reflection.
Maybe this part is a 100& reflective surface with an alpha channel applied to create the pattern? Seems like a lot of work to me. I would maybe just make the surface a breakup of all of the lighting tones you are using, in the glow channel. After all, if the effect is specular, which is going to be the brightest thing in your picture anyway, why waste all that computation time with a light emitter to catch the reflections etc.. If I was only doing one shot, say the wide shot of the drop, I'd see if I could make a mask that you could use in PS to touch up the render.