I started with 350 grit but needed to go lower to even things out. I moved up in increments until I hit 620 grit but will probably stop there. My worry was that the bowl is too smooth at that grit. It still needs some evening out, but my focus now is mostly on the transition from the bowl to the rim. The rim wasn't quite even. I am not trying to detract from his original piece, but give it some finishing touches that I felt was missing. Since the uneven bowl would most likely interfere with the smoking experience, I don't feel like my alterations are misplaced.
I will upload a picture when I am all done. It's been fun sofar.