Make a frame to support a clampy thing I got at Oshkosh a while ago and don't use much. It makes JUST enough of a drill press to make the pattern instead of polish. I hot glued some scotchbrite onto 2" diameter work wheels and drop and release with one hand and move and support the metal with the other. I marked a 1" grid, then put 1/2" hack marks every second line.
Started out with lines parallel to the upper surface, then transferred the lines to the center firewall piece, adjusting to the vertical parallel to the centerline.
This is the first genuinely joyful thing I have done with metal on this aircraft!!! Very happy with result, but very tired and don't want to screw up the finale!