I would do as 2knife said and use 000 or 0000 steel wool and WD40 to get as much off as I could. Then follow up with flitz or neverdull, etc. The pitting will stay, you will not get rid of it without taking down the blade steel, and nothing mentioned above will do that. Anyway, the pitting doesn;t bother anything except the aesthetics, and sometimes it's better to leave it than take the blade steel down so far it changes the shape of the blade (thickness-wise).
I know you want powertool-less solutions, but really, once you've got most of it off with what's been mentioned, nothing helps more than a muslim buffing wheel charged with tripoli or other rouge.