If you're familiar with the Big Jim "Black Book" he says to align each hood individually by tweaking it then running the motor and looking at the wear mark on a test brush until it's centered.
I've tried that method, and I have to conclude that I just don't have the touch or skill to get it right that way.
What I do is to take an alignment bar, the kind that takes a rod through it and the bushings (I use a Trinity bar) and put it in the hoods and the bar through the bushings, then I loosen the spring posts and hood screws, then crank each hood clockwise against the bar and retighten the hardware. If I've done it right, when I try to remove the bar, it feels as though the hoods are trying to hold on to it...
I didn't come up with this method, I read about it on Hobbytalk. It seems to work real well for me.