I'd say start with 10 passes on the Naniwa 12 and see what that does. If it gets you close, try 10 more. If it doesn't get you close, some time on the 8k or maybe conservative pyramids on the 4 and 8k and then up to the Nani 12.
It really depends on how far from "shave ready" you are.
+1 from me but may really like +50---- meaning I don't think you could damage your razor if you rubbed it on that 12k for a month. I like a little lather or dishwash detergent on mine, and lots of strokes, mixing up circles and x's.