To keep your hands from smelling like gasoline or diesel fuel when working on your vehicle, do the following
Prevention#
Use a Barrier#
Wear gloves. Your hands are going to get the most exposure to fuel, so wear a pair of nitrile gloves. They're cheap and your skin will thank you. Even better, wear longer gloves, like dishwasher length, or longer.
Wear Eye Protection#
Getting fuel in your eyes is really bad. Your first reaction will be to rub them. With your hands. This will spread even more fuel on them. Even if you have running water on hand, the instant fuel touches your eyes or skin, it starts getting absorbed.
That said, having a source of gently running water on hand is a good idea.
Pre-Soak Your Skin#
If you're going to be working in the shop all day, and you don't have gloves as long as your arms, you're still going to get the fuel on your skin.
The next best thing is to pre-soak your skin with tons of oil - vegetable oil, shortening, whatever. If your skin is saturated with oil, it makes it much more difficult for the fuel to absorb. Regular lotion won't do it! Most are water based.
Cure#
So you're already dirty. Now what?
Easy Access#
Wash your hands and arms with dish soap. Use plenty of it. Without water! Afterwards, repair the skin with lots of lotion.
You can also wash your hands in vinegar.