Been experimenting with kolrosing recently.
For a tutorial, see Del Stubbs' site. Basically you cut a line into the wood and drive pigment in (ground coffee works great, though I am experimenting with other effects.) I am still working out a system so that my left thumb does not hurt so much as I push/lever the blade along. I want to find a thimble that will fit my thumb, but no luck yet. When finished you need to remove the excess pigment to reveal the lines beneath. I have been shaving the surface with my knife, which leaves a nice, crisp line so long as you don't go too deep. Others sand the surface to reveal the line, but I never got as crisp a result with sanding. That said, Jarrod Stone Dahl suggested that sanding serves an additional purpose. It folds fibers over the cut and helps keep the pigment in place. I did have some pigment fall out on the two right-most spoons, so maybe I will try that again. He also said burnishing would do the same. Must experiment with that.
Also, I have not tried sealing the wood, as suggested on Del Stubbs' tutorial. Should try that as well.
Oh, here is another great resource: