Do you know of any equipment that would remove graphite residue from the graphite piece? In the best-case scenario, the residue is graphite dust, worst-case scenario, residue is graphite dust mixed with EDM oil. F.V.
It is a difficult to answer this question without more information on the part or the cleanliness requirements. I would think mechanical action would be the most beneficial to cleaning your parts. Some possibilities would include spray, spray under immersion and ultrasonics.