Another job I did, was to fit the ferrules and run the ground wire.
This was fun.
I tried to solder the wire to the bottom of the ferrule, but it didn't work. The pressure of pushing the ferrule in the body was breaking the soldering.
Then I decided to twist the wire around the ferrule, and push it in
.
This almost worked, but it was too hard to push the ferrule down ground with the wire twisted like that around the ferrule.
What worked at the end, I forgot to take a photo but it's a solution similar to the one pictured above.
I made a sort of little spring with the exposed wire twisting it around with small pliers. Put the ground wire/spring in the slot, and pushed the ferrule in.
I measured with a multimeter and it was fine. I proceeded like that for all 4x ferrules, checking with a multimeter, it worked!