Recently adjusted the handbrakes on the Monza and Omega and both are now fully set on the 4th notch. I had to fiddle around with the cable adjustment on the Monza because I'd slackened it to remove the trailing arms, but on the Omega I just put the screwdriver through the hole and turned the adjuster. Took some doing as the nearside needed the wheel turning upwards to tighten the brake up and offside needed downward adjustment for the same effect!
I did mine in the dark with an anglepoise lamp on an extension lead directed through the hole at the adjuster, out of necessity not design, but it did allow me to see what the adjusters were doing: if the adjuster is being turned to tighten up the brake, you expose the thread on the adjuster as you turn because the adjuster 'expands' to push the shoes against the inside of the discs. If you're backing the brakes off, the thread will disappear.
As others have said, all this is done with handbrake disengaged. I tested mine by pulling the brake on occasionally and bolting a wheel on to give me enough leverage to grab and heave and see if I could move it!
I didn't look at the condition of my shoes, would have known to if the adjustment had made little or no difference I guess.