[Speedslug]

When I was soldering electronic components back in the day...

We used needle nosed pliers with rubber bands around the handles and pinched the part we were soldering with them.

They would effectively steal the heat to keep it from going past the them and prevent other solder joints from coming loose.

If you are quick enough and the joints are clean and have flux to prevent the oxidation from spoiling the joint you can even use alligator clips but you do have to be rather quick as the thin metal of alligator clips don't soak up much heat.


Another trick you can do is to wrap previously soldered joints tightly with soft copper wire and you can then weave this wire from one joint to the next and the next with each one getting a good solid full wrap before going on to the next.


And other thought that just came to mind might be to try precious metal clay as a packing around already soldered joints. We did not have it back in my day but it is mostly metal powder and should wick the heat away. Just a thought. Good luck.