Pull measurements from the adjacent panels to find the centerline of the can (x & y axis). Mark the centerline on the new panel, making sure you take into account the proper orientation of the panel once hung. Use a compass to draw your circular cut line. Make it slightly larger but still close enough to actual diameter that the scussion covers it. If you're matching existing 1/4" panel, I'd use a jigsaw with a fine blade to cut the hole. Hang panel. Wash, rinse, repeat.

Drywallers use a router. They'll hang the sheet, find the approximate location and do a plunge cut. Find the edge and follow it around.