FWIW, my original (and expensive) Modernist Cuisine steel has a decidedly rough, textured surface, which worked fine. Almost "pebbley", like a new cast iron skillet.
I sanded an unfinished steel plate with an orbital sander with an 80-grit pad. It produced a nice uniform pattern that worked fine as well. I use semolina on the peel for launching - wheat or rice flour might be a different story.
What if you used a coarse grit to get the "hills and valleys", then a quick pass with very fine grit (like 400 or 600) or even steel wool to knock off the sharp peaks? I would bet money that this would work for you.