Diagnosing high voltage

What we are trying to say:

Seems like you have the trouble localized. Time to yank the alternator
Look at the brush terminals. Take them apart. Look for broken/ missing insulators/ hardware. If that does not result in an answer, then remove the brushes and holders completely, and with one probe on the case, probe either available slip ring directly. If you get ANY continuity to the case the rotor is grounded. Otherwise, look to fix the broken brush assembly, or replace the alternator.

I'm with Mattox. I rarely try to memorize "step one, two three" troubleshoot procedures, except "generally." Start somewhere and go left to right, up or down. Try to keep in mind "the path." Where does it start, where does it end, what is the desired end for the effect and so on. Don't be afraid to get frustrated, drop that line of thought, and "rethink."