There are some folks reading this blog who like to see the step-by-step version of things. So here's how I built out the ceiling over the hallway ductwork. After I took down the recessed lights (which were positioned up in the joists by the electrician, who did his work before the HVAC guys placed their ducts), I ripped some 2x4s down to 2x1s, and nailed one set at the appropriate height along the wall, and another set on the joists next to the ductwork:


I cut OSB to size for the "side" of the ceiling (the side of the hallway will be closets, where the ceiling will remain open for now) and nailed it to the top bracket:




Set the studs:


Replaced the recessed lights:


And hung the sheetrock:


This is an essential tool for an drywall project with ceiling work - cuts nice clean holes for your ceiling penetrations:


And voila! Hallway is ready for tape and mud.