I just started playing guitar myself, but I teach court reporting, which requires an almost superhuman dexterity and speed (and no, I don't do it myself) and, like playing chords in music, a sound (syllable) is written by simultaneously depressing groups of keys, sometimes in awkward positions, on the stenomachine. It's very similar to playing a musical instrument (and they have to write 225 words per minute accurately to become certified!). One of the things court reporting students sometimes do to increase their speed, strength, and coordination is to work on the strength of each individual finger and then groups of fingers in different combinations. The little strength-building devices sold to rock climbers (Gripmaster, Prohands, etc.) work well. Even a thick rubber band can be used (try letting one finger at a time pull against the rubber band). Most of us have weak ring and pinkie fingers. Strengthening the fingers and practicing moving each finger individual of the others against resistance can really help their accuracy and speed in writing.