If you're going for a mirror polish, the easiest way I've found is 60 grit (cubitron), 220 grit (3m 707E) to take out all the 60 scratches, 30micron AO belt (372L) , 15 mic finishing belt (372L), 1000 grit hand sand against the belt scratch direction, and buff with green chrome. If you're working with a flat platen and can't use a wheel, structured abrasive belts or more time with hand sanding to get up to clean 1000 grit work as a substitute for the micron belts (the 220, 400, 1000 progression works great for me). The micron belts are a plastic film and so thin that their joint leaves a bad bump mark every time it comes around.
The jump from 1000 grit to green chrome on a 3600 rpm buffer (sewn wheel) leaves a fantastic finish. I like the Cubitron belts more than Blaze and just ordered a batch of those 984F "cubitron II" belts with great anticipation. Maybe soon it won't kill a whole belt per 8" blade doing the rough grinding on hardened steel.
Simple answer: if you can't get a scratch out with the grit you're using, you're using too fine a grit. Go back a step or two. It's tough to do, but it's tougher to take a 60 grit scratch out with a ~600 grit belt and not overheat the blade or otherwise mess something up out of frustration.