I've been playing about with refurbs lately trying to find the secret formula - the best I've managed so far was using 80, 120, 180, 240 grit.
All 4 stages were done using my sander, nothing by hand, at varying speeds. The finish has actually come out really nice with no old sticker marks showing through. I'm just waiting on my polishing compound to arrive at the moment so once I've got that I should be able to get the finish nailed down too! The ones I've done look good enough to go as it is, I just want to add a bit of extra sheen with the compound
I know some on here go as far as 400 grit, but personally I think it's probably a bit overkill (but then if you're not going to use a polishing compound it'll probably make a difference).