Once you've set your dark tones you can make them lighter by altering the exposure, just as you would with highlight exposure. This is where experience and 'expertise' comes into play and it's no harder than doing the G.00 exposure first..
I don't understand what you mean by making set dark tones lighter by altering the exposure? Are you speaking of the second exposure at G.00 being altered? How do you lighten an exposure by adding to it? Or are you suggesting dodging the the first (G.5) exposure and making it lighter? I'm not trying to be PITA but I don't understand what you mean,