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Hanging out in pawn shops will definitely lead to something bad. Using a Dremel to work on old straight razors can lead to far worse: broken blades, burnt scales, nicked scales, and in the worse...

Since these are all brand-new and well-honed blades, I'd say yes to the N12k now. That should be all you need for touch-ups. It's a surprisingly fast stone for its grit size.

As far as working on...

I hope you'll never need that 220 side. You will, as Niftyshaving said, need a 325-grit DMT plate to flatten (or lap) your hones. You'll need to do this before you use any of them; from the factory...