He's either talking about high voltage, where the charge repels itself out to the surface, or about about alternating current skin effect, which only becomes a concern for normal wire sizes at frequencies in the tens of kilohertz and up, and for which the added conductivity is only slight in standard strands, because they increase the wire surface area. Litz wire, which has individually insulated strands does a bit better.
Ferrous metal has iron in it. Non-ferrous metal does not. Ferrous comes from the Latin for fur, because smiting your enemy with iron weapons was thought to put hair on your chest.
As to the Faraday shield, most of us who've been in instrument design depend on them. They have a shortcoming, though. Many a shielded piece of electronics has been blown when its shielding chassis was struck by lightning. The electrical field in that instance is so great that the momentary difference between the voltage at one end of the shield and the other, as the electrical field propagates over the surface, can induce damaging voltages on the enclosed circuit. Devices in danger from lightning or other strong electrostatic strike often require double Faraday shielding, with the inner shield tied to just one point in the outer shield. That attenuates the damaging induced voltage considerably, though not 100%. Under some extreme conditions even a tertiary shield may be required.
Cartridges are pretty safe. They are not easily fired by static charges. It is possible for an electric discharge to fire a finished metallic cartridge by heat, if the spark is strong enough or plays on the primer long enough. It is also possible, theoretically, to hit the primer with charge so fast it drives an arc from the cup to the anvil via capacitive charging, but it takes some serious juice applied very, very rapidly, indeed. Accidental static discharge will not readily fire cartridges, or they would go off spontaneously in aircraft all the time.