Depending on the steel chemistry and how much stuff there is to see in the final finish, anything from 600 grit to 2000 grit works well. I have a Gunto that I am remounting and repolishing for my wife and a 2000 grit finish before the etch was awesome.
I usually make a sanding block of gum eraser rubber and use that and cutting oil as a final finish. Slow, precise, full length strokes and I position my hand so that the block does not wander. I use the middle finger of my left hand to ride along the back of the blade so that all of the 2000 grit scratches are parallel and consistant. Then I spray the blade heavily with pressurized anhydrous isopropyl to flush any stray grit and oil off the blade. Followed by a running water bath with dish soap (cold water).
I etched by making a solution of vinegar, filtered water, lemon juice, and dish soap in an aluminum deep pan heating to boiling, and then suspending the blade point down (held in left hand) so that I can dip and brush the boiling solution over both sides of the blade with a fresh paint brush. When the blade is black, it is washed with running water and dishsoap and clamped in a Panavise, and a solution of mineral oil and a little bit of Pikal was used to remove all of the black oxides. This made the whole sword frosty and hid any remaining little scratches. About 5 rounds of etch and polish.
Then the back of the blade is burnished with a polished burnishing rod to increase the contrast and visual appeal of everything above the ridgeline. Then I masked the tip of the blade making a heavy line of masking tape at the yokote and counter polished the point with 1500 paper and oil on a rubber block. I don't have pix of the blade but it is very attractive and functional. It is a hand made gunto of monosteel and the edge is very hard and very attractive.
On this particular blade, 2000 grit single direction followed by an etch looked very nice. Also, experiment with concentrations of various types of acids. Weaker acids, used hot or in multiple cycles work better on many blades than a single etch in ferric or whatever in my experience. But every blade, every different steel, and every different heat treat scenareo will make its own demands. Ya gott get jiggy with it and exeriment with an open mind and a full toolbox of alternative ideas.