I have recently acquired a Vivitar 285 and im goin to be using it with my Bronica SQ-A. Unfortunately i dont have a flash light meter. is it possible i can use the 4 coloured auto settings on my flash with a sync speed around 1/125 on my SQ-A, setting the aperture on my camera to the same as the aperture on my flash and letting the flash auto sensor get the correct exposure?

thanks for your help in advance.