I use rear sync but not as often as the method I described. With rear sync, the camera is in charge of the balance. With that method, the camera will often also try to adjust the background to a middle gray and in this case that would not be my choice.
I prefer to set the background exposure to my own liking. In this case at a level that just lets the post-dusk sun-glow leak through. The CLS lighting system on the camera/strobe then provides the foreground/subject illumination balance.
Roger It's still, ISO, aperture and shutter-speed, right?