Below are some of the video lessons available for mandolin and violin. You can also view all of the video lesson Playlists in one location. In addition to lessons, I have uploaded dozens of example of tunes and songs on my YouTube Channel.
Mandolin Lesson - Picking Patterns
Shifting into 3rd Position on the Mandolin
Shifting into 4th Position on the Mandolin
3rd & 4th Position Shifting on the Violin