Here is a simple addition that helped me to locate holes quicker. Others have added a laser cross hair, but this method doesn't require batteries and is cheap to boot. It consists of a short piece of insulated copper wire with a jewelry bead epoxied to the end. The whole affair is attached with some 100mph duct tape and can be easily adjusted using simple finger pressure.
I adjust the bead so it floats close to the edge of where the dimple die pin is located. When the piston is lowered, the bead gets pushed to the side and snaps back to position when the piston is raised. The wire is flexible enough so that I can easily move the wing skin around, but as I get close to aligning the next hole the bead accurately indicates where the pin is. This simple device easily doubled my dimpling speed. (Yes- I've been warned about dimpling with the plastic still on).