I'm a big believer in finger drills. When court reporting students practice moving between tough fingering positions, it cuts down on hesitation, which ultimately translates into gained speed.
So for your practicing pleasure, here are a few drills focusing on tough left hand strokes. I recommend practicing one 4x4 group at a time, doing several repetitions, and then moving on to the next one. Try these at the end of your next practice session! You can also stroke these against a metronome (like this free online metronome) for maximum results.