|Henry Schradieck is the topic of today's History page. He was known for tremendous emphasis on fingering exercises.
Here is a finger exercise you can do even if you are miles away from your instrument.
Hold a sheet of newspaper by the corner using your fingers with your arm stretched straight out in front of you. Using the fingers alone, attempt to ball up the newspaper into your hand while keeping the arm stretched out straight. Be sure to use only one hand, do not use your other hand for assistance. Do this as quickly as you can and repeat it with a fresh sheet of newspaper (if no one needs to read it!) until your arm, hand, and fingers become fatigued. Gradually, this will help you build endurance and speed. Use the large sheet from a full-sized newspaper like the NY Times or Chicago Tribune rather than a tabloid. Crumble a newspaper sheet with one hand. If your hands are in good shape, it will seem easy, but you may be surprised how hard this is by the time you're done with the fourth or fifth sheet of paper!