I wanted to repeat my "wiring tip #2" again, and with a bit more information.
The technique works REALLY well!
Today, I had to make a wiring harness that connected a 12GA battery wire to (quan) 4 14GA wires (ESCs).
The technique below mentions 12GA and 14GA wires, but it will work for any wires, small or large.
Strip about 3/8" insulation off the ends of all wires and twist each one tight. I recommend that you do not 'tin' them, and do not twist the several ends together at this point.
Strip about 4" of the insulation off some 30Ga KYNAR insulated wire (solid wire commonly used for wire wrapping).
Hold the 30GA wire (the part that still has insulation) in your hand and wrap 4 turns of the bare 30GA around the 12GA wire. Then take one of the 14GA wires and lay the stripped end next to the stripped end of the 12GA wire (but in the opposite direction - overlapping only the stripped sections. It may help to use a medium-sized hemostat to help hold them together (but it can be done without a hemostat). Now wrap the remaining 30GA wire around both the 12G and the 14GA wires.
Strip some more 30GA wire. Wrap 3-4 turns around the splice and add a second 14GA wire. Now wrap the 30GA wire around all 3 wires. Do the same for each wire you have.
Now solder. Because the wires were not previously tinned, they will take a lot of solder. I recommended that you do not pre-tin the wires because the solder adds bulk, and will prevent the wires from fitting tightly together, resulting in a larger joint.
I think you will find that this technique works remarkably well.