I would advise start lower than 100 circles, 20 each way and 10 x -strokes, if its not enough do another 20/10. typically you can see the slurry color change that means you are getting there. when I see change in color I start diluting for 10 circles each way dilute again and so forth until I end up with 10 x strokes with water only. All the numbers I mentioned can vary for the particular stone.
I have used 4 different Iwasaki Choice stones and all of them have been great finishers.