He's not talkin' about tarnish here, buddy. He's talkin' about a carbon buildup from arcing.
Looked like tarnish to me. Of course the real issue is letting it go that far. Wiping off regularly with glass cleaner or mild polish would prevent most if not all of it.
Some protection, like NO-OX-ID A-Special , other dielectric grease, or what's in polishes like Blitz is certainly a worthwhile addition.
I quit using Brasso years ago. Just too abrasive for what I clean.
Nevr-dull would have cleaned those 3
mods nearly as fast, and needed less post cleaning work. Sadly, like Brasso, it doesn't really inhibit future corrosion.
The way
mods are handled, any protective coatings will wear off quick. Regular cleaning and protection us a must for any metal that corrodes (copper, brass, aluminum, steel).