I've learned that metallic paints highlight and magnify details and blemishes, so I needed the model to have a very smooth surface. To achieve a smooth finish, I sanded the model to remove minor imperfections, and filled low areas with a two-part putty.
In the process above, I also removed all of the details from the wings. I needed to replace them. To do this, I placed label tape on the model and etched some panel lines. The backside of the tip of a hobby knife served as my scribing tool. The label tape makes a nice guide because it is self-adhesive, is straight enough for my needs, is flexible, and offers a ridge that helps guide the scribing tool.
Once I finished the panel lines, I lightly sanded the model with very fine sandpaper.