So, I clearly should have asked this first but...

Any tips or tricks for repairing vintage leaf springs?

I wasn't getting continuity across the leaves when closed. Cleaning the metal leaves with a little naval jelly fixed that.

Then I tried to remove the old wires and solder ones in their place

First one went OK, barely gave me any trouble. I tinned my wires, jammed them in where the old wires used to be, hit it with the soldering iron and I was good to go.

Second one was a totally different story. I couldn't get the new wires to solder onto the leaves for anything. I ended up melting the plastic housing of the switch. I abandoned it and just installed a modern micro switch instead.

My lights are working, but I'd like to know what I did wrong.

In retrospect, if I'd known how tricky it was going to be, I'd have left a stub of old wire and just soldered my new wire onto that. But is that the only way? I'm guessing a few of you have been down this road already. Hoping you can steer me right for next time around.