In order of severity of gunk: Hand soap, Dr Bronners, citrus degreaser, gojo orange w/o pumice, Snap-On Hand cleaner.
as far as I can tell these are all environmentally friendly with even the Snap-On being soy based with Walnut shell abrasive. (I looked for a link for the Snap-On cleaner and it doesn't seem that they sell it anymore, Oh well, atleast I have a case left.) I have yet to find a bicycle mess that these couldn't clean. I also used these on the nasty greases and filthy messes I would get into when I was a Crew Chief in the USAF. Even the nastiest of combinations of hydraulic fluid, oil, brake dust, jet fuel, and grease would be cleaned by two vigorous scrubbings with the Snap-On stuff. GoJo with pumice is a somewhat adequate substitute for the Snap-On cleaner.
Nothing I've ever found gets the diesel fuel odor off, but the juice from a fresh lemon hides it pretty effectively.
I made some soap a while back that I used espresso ground coffee in, that covered the smell up pretty well, and was a good abrasive for getting the gunk off.