In the past whenever I've been tweaking derailleurs I've always pulled the actual derailleur wire itself to move the derailleur, like to set limit screws and clearances, so that I'm eliminating the cable tension variable. But I can't do this with my new bike with internal cable routing, because there's only a couple inches of wire accessible in a very awkward spot, and then I can't turn the pedals at the same time because my hand is in the way.

How do people get around this? Or do they just live with it and just do endless back and forth trial and error with cable tension and limit screws etc?