Finger vibrato is very useful when playing 16th notes that need color.
It is a combination of wrist and finger, back and forth quick motion. It is important to allow the first and second finger joint to be flexible, curve, and straighten.  Your finger tip should roll back and forth smoothly and evenly. Vibratos should vary in speed, width and intensity depending on the type of music being performed and desired flexibility. Apply more weight to the left side of your left hand fingers for better strength and angles.