Practice
How to use and practise it
Vamp between the minor chord on the root and the major chord a fourth above it, and let the major 6th sing. Compare with the natural minor positions: only one note per octave moves.
Same notes, another root: C major. The shapes on the neck are the same; only the note you start and end on changes.
The natural minor has a minor 6th; Dorian raises it to a major 6th. Compare the two: D natural minor.
Set the tempo low, play each position up and down with the button above, then try it yourself at the same speed. Raise the tempo by 4 BPM only when it is clean.