What ever you decide,,, suggest cleaning away the black residue,,, it is particles of steel and does not contribute to sharpening process. It will delay steel removal and frustrate apex formation.
Good magnification will decide micro, macro, dubbing,,, a lot of postings without real observations are misleading. I found a nice condition Nikon microscope 10x-80x on the big auction site,,, very interesting to actually examine some of the popular eye wash stories for strops and dubbing.
Regards,
FK