Quote - I don't know why everyone keeps telling people who are trying to learn that they are going to have to "hand paint" everything.  From what I have seen, most of the bump maps are grey-scaled images of the original with eyebrows, veins, moles, etc. corrected.

(Once again with feeling) The greyscale version of a colour texture is not a proper bump map.
The variations in colour do not equate to ups and downs in the skin surface. You'll find that most of these bump map are applied in very small amounts, and would fail the true test of a bump map, which is if applied as a displacement map with a realistic maximum, would give a sensible result.