Hey Scott,
That was very generous of you to post so detailed a response regarding short detection!
This all makes sense to me. In effect, your described technique will re-establish the #15 circuit using the multimeter/ohm meter without the battery inline. It's all so simple once someone spells it out as you have.
Looking at the electrical schematics, I see that most of the paths fed from the #15 fuse branch from connector "X18", located in the driver's footwell near the parking brake. That seems like a logical starting point for my investigation.
Thanks again for the primer!