600-800 grit then 1200 or 1500 then something very fine like 2000 or even 3000 - all wet sand. If they aren't heavily oxidized, you can really skip the 600-800. If it's the scratches you are worried about mainly, I'd just go longer with 1200-1500 and avoid using 600-800 again. 1200 will get it done quick, 1500 will take bit longer but the 2000-3000, you won't have to work as hard.
4-8-12-15-2k is a lot unless you are dealing with like thick toenail fungus colored oxidation. Just my opinion, there isn't enough of a difference to make a difference by using both 12 and 15, and both 4 and 8 are intensely aggressive, so why use both?