Having to work on diesels, with that BLACK carbon-filled oil, I have
found that a good-quality dish detergent (Palmolive, Sunlight or
similar) gets rid of the worst of it, with a good go with a nailbrush
(the masoschists out there could use a wire brush).

Then I use Solvol soap, the pumice-filled one. Those who are into
"exfoliation" should enjoy this stuff... use it in the shower too, for
that refreshing feeling of raw bleeding skin.

If the grunge is really bad, washing hands with a solvent like
gasoline or turpentine before the detergent works well.

Orange-based detergents do not work any better than far cheaper dish
detergents. Neither do commercial gel cleaners such as Swarfega, so
favored by mechanical workshops; these also leave an oily residue on
the skin.