Is the prep stone a white square about 3"s long and 1/2" x1/2" ? If so it's like a slurry stone, use it on the 4k and or 8k. It also works good to get rid of stone loading.

In the circles I tend to run in, Nortons are notoriously not flat. So use the flatened and a pencil grid to make sure the stones are flat from the start. Don't worry to much about the 220 being flat at first. But make sure it's flat after you use it. Most 220 stones are fast wearing stones and need to be flattened after use.

Now thats in my circles, kitchen knife circles, razors don't put as much wear and tear on stones like 12" AS steel knives and such, so take this all with a grain of salt