"Make sure you release the pressure of the finger before shifting and listen for the new note before putting the finger down again. Make sure that the elbow swings to the right while shifting up and back to the left while shifting down again."
Enjoy the sound of shifting in this E minor arpeggio on one string. Shift calmly and keep the bow moving during each shift. Listen for your arrival note, which you can hear even though there is only harmonic touch. Hover on the arrival note to make sure you are in the correct place before increasing the finger pressure enough for the normal note to sound.
Notice that as you release the finger pressure the thumb also releases allowing the shift to move freely.
This exercise is good for an 'over-energised' shifter who always arrives with a great deal of fuss, but not necessarily much accuracy!
In performance the faster the speed of the shift, the less time (and need) there is to release the finger.
Shifting - Introduction - for Tempo
Scores - One-Finger Arpeggio - violin & viola