Step 2: Plug Wrapping
The goal of this step is to get the washers fitting tightly around the barrel of the power connector. The washers will be a little loose around the barrel, so you need to cram in enough copper to get them to make a good connection with the barrel.
Cut a strip of copper sheeting and wrap it around the barrel, making it long enough that the washers will just barely slide on over it. Some trial and error will be necessary in this process. I eventually figured out that about three and a half wraps of sheeting worked best.