right angle transistion

I understand that transition flashing is used for a pitch change with panels running in the same direction. What is "best" practice for transitions with panels running at right angles? I have two steeper roof sections at right angles to each other with a valley in between. Both sections (and valley) transition into a common, lower slope roof section. The panels on this lower slope section will be parallel to one of the two steeper roof sections but perpendicular to the other. Do I use a combination of transition flashing onto a Z-bar which then overhangs the perpendicular panel? (Existing roof is shingle so no guidance there.) Thanks.