I work in biometric fingerprinting (we sell the hardware and software, which we developed, for state and federal background check digital fingerprint submission). Optical fingerprint scanners do not work well on dry fingers. Almost everyone will need some kind of ridge builder.
If you make sure to keep your hands moisturized in general it should make a difference, as should holding your finger on the scanner for a 2-count or so.
We recommend Corn Huskers Lotion because it's inexpensive, non-greasy, and a small amount will keep your hands moisturized for hours. In a pinch you can swipe your finger on your forehead or nose and pick up a little skin oil.