Run the stud finder across the ceiling and mark each joist. Mark the positions of the studs across the whole ceiling with a level and pencil.
Measure along the edge of the ceiling where you want to start, which must be perpendicular to the joists. Mark that measurement on a 1-by-6-inch ceiling plank. Cut the plank at that length, straight across, using a miter saw.
Set the board against the ceiling with the grooved side facing the wall and sitting ½ inch out from it. Nail it in place with a nail gun, shooting the nails straight up through the face and into the joists above. Use two nails per joist.
Cut the next board to the same size. Press the grooved side of the board to the tongue side of the previous board. Nail the second board through the exposed side rather than the face, shooting the nails at an inside angle from just above the tongue, one per each joist.
Repeat for each board, working across the ceiling. Cut the final board lengthwise on a table saw to fit along the ending wall with a ½-inch gap there. Ceiling trim will cover the gaps.