You mention "green fuzzies to start forming inside of the harness". If there is a harness, you can insert your probe into it without probing the insulation of the wire. But what if there is no harness near in the wire you want to probe? The pick probing technique I recommended it not at all using the fatness of a pin. The probe used is like that of a very slender needle. In fact you could probably actually use a fine needle and attach an alligator clip to it to get a reading. The "hole" made in the wire is so miniscule as not to cause a problem of corrosion or a grounding hazard.
BTW, I said "heftier" than a pin - but by that I mean stronger, not heavier or fatter.