Vibrato can be used to improve shifting clarity and control.
Firstly use vibrato on the note before the shift, then the note after the shift and then both the note before and the note after.
The note before a shift sometimes loses clarity as finger pressure is released too early in anticipation of the shift. Although the time taken for a shift does come from the preceding note, make sure that this note is still clear.
Vibrato can also release tension in the hand.
These vibrato practice techniques can be used in all shifting exercises, such as Yost.
Resources - Repertoire
- for Exercises for Change of Position by Gaylord Yost
Scores - Use Vibrato as a Practice Technique - violin & viola