Just start sharpening any knife, but don't rinse away the mud after and use worn sand paper or a cloth to transfer it to the blade you want to polish and have at it. That's what I'd do. Or you could generate some with a lapping block or diamond plate or nagura. We had some discussion a while ago on my 'Tips on Polishing' thread about how various grit ranges work out - stones vs sandpaper, etc - and turns out the system is impossible to figure out, or so it seems to me, so I'm not sure what 1200 grit paper relates to with stones (it might not be equal to a 1200 stone, for example). Anyway, I haven't tried polishing with stone mud, but I hear a red Aoto is good for this; I have one and the grit range seems to be in the low thousands.