Definately take a sander/grinder to a cast iron to make a MIRROR finish and then season it...
This does nothing but improve cast iron cookware. Even badly rusted cast iron utensil can be restored using an angle grinder unless it has holes in it. In that case drill some more holes and call it a colendar. I usually start with a wire cup brush. If that doesn't smooth it up a flap disc works well and you can get different grits. I wouldn't use a grinding wheel. A hand sander will work also.
