Mach Two
Not sure how you guys were taught to spit polish but the way I was taught - by an Ex RSM where if you weren't up to his standard it wasn't good enough - spit polish multiple layers of polish onto the shoe until you get that lovely deep mirror finish shine.
Now once you have this, if you get a LIGHT scuff on them, a piece of nylon stocking wiped or buffed over will take it back to it's former glory. I think it has to go with the fine nylon and very close weave but I can assure you it worked for me for years.
I'm sure others have other ways that work but that's what I used.
Hope that helps.
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