For graphite we recommend the Norax belt or the Micro Grit Belts. Our guys, who prep hundreds of shafts a day, have the skill to use the sanding belts on graphite and steel. Usually the medium sanding belt is on our production machines and is used for both steel and graphite. You have to be highly skilled with a good feel to use the sanding belts on graphite when using a sanding machine. doesn’t take much to mess up a graphite. If you are prepping by hand, using a fine grit is OK for graphite, medium probably for steel. If you are using a sanding machine, I think the Norax or the Micro Grit belts are the safest to use on graphite.
To get a uniform look requires consistent pressure, without cutting into the material. You can measure the bore depths then tape the shafts to get a clean prep line.