Valve adjustment

I'm building a slant and am ready to adjust the valves; the engine is sitting on a stand, so obviously I need to set them cold. I remember from back in the day that there was a procedure that allowed you to set valves on a 6 and only turn the crank 3 times - each cylinder has a "companion cylinder" and you can set 2 at once. I just don't remember how to tell which cyls are companions. Anybody remember how this is done?