Thanks!
Hamon etching - I like ferric chloride diluted with three parts distilled water and a few drops of dish soap. Lemon juice can work nicely too.
Etch, sand... repeat as you work your way up the steps. I'd try to finish somewhere between 600-1000 grit. 600 will give you a nice look and 1000 will bring out more clouds. Try sanding above or below the hamon, 0000 steel wool, flitz... I like to bring out some contrast with acid (scid then sand over many cycles) then use Flitz to polish the bright part.
Nick Wheeler has an incredible tutorial on hamon etching he has done here... check that out for sure. His info is way better than mine!