I am dealing with new students not shifting well to positions and felt the need for a simple exercise exclusively for practicing and learning third position shifts.
Practice shifting from first to third position slowly at first. Slide on each finger from first to first, second to second, and third to third and steadily increase tempo for best results.
Try to memorize the feeling of where your hand ends up, either by feeling a guide when reaching the position or by memorizing the feeling in your left elbow when bent the proper amount. Remember to rely strongly on your hearing both in anticipation and arrival to the note.
Third Posistion Smears by Fiddlerman
For more help watch the third position video below: