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Don't use regular sandpaper. What you want to use is lapping film. You can get a pack of 10 sheets on Amazon with grits that range from 250grit-500,000grit. This stuff is seriously the best for polishing/sharpening. I've used it on multiple knives that ended up so sharp I cut my finger down to the bone with very little pressure while whittling. Lapping Film
This one is $24, at least for me it is https://www.amazon.com/dp/B074DK653S/ref=cm_sw_r_apan_i_ND9661PX2MEYKVDV68V