Resetting up my disc brakes after cable stretch, and with Shimano its these steps.
Loosen 2 brake caliper bolts, insert Shimano TL-BR51 spacer between outside pad and rotor
Tighten wheel side pad till it touches rotor
tighten mount bolts
pull out spacer
back out wheel side pad a click or two.
Very very simple. Just happens that a matchbook cover is the perfect spacer. Found this out when I couldnt locate my old feeler gauges.