Bob Ludwig, Doug Sax, Bernie Grundman - they're masters of mastering. They produce hit after hit, with nothing at their disposal other than...well, experience, talent, great ears, the right gear, and superb acoustics.
I rely a lot on the meters. I've used CurveEQ and Har-Bal. I like how on Har-Bal that you can zoom in really close to draw the curve you want but it's inconvenient that you it's a standalone app and not a plugin because you can't hear it as you're making the changes. What I prefer to use nowadays is the TC Electronic Assimilator plugin for PowerCore. IMO it has the highest fidelity of those three. It's not as granular as Har-Bal because the window is a smaller. I don't draw that much though, rather I usually go off some solid reference curves. It's black magic LOL.