Watch the Guide Change online guitar lesson by Brad Carlton from Chord Studies: Jazz Turnarounds Vol. 4
In this example you have five voices in each chord and you'll be skipping some strings. While playing the Fmaj7 rest the first finger on the sixth string to deaden it, and that way it will become a guide finger as you move into the Abmaj9. Try hybrid picking this example: hit the bass note with the pick and grab three adjacent strings in the upper voices with fingers 02, 03 and 04.