Another method of wiring connectors with lots of contacts is resistance soldering where a tweezer-type tool heats the connection with a very low voltage, moderately high current that passes thru the contact's solder cup, creating very localized heat.
The wire ends are stripped and tinned, and the solder cups at the ends of the contacts are tinned and partially filled with solder.
The tweezers are "pinched" onto the contact (each side of the solder cup), the resistance soldering station is energized (foot switch, typically), and the tinned wire end is pushed into the molten solder puddle in the cup as the heat increases to the flow temperature of the solder.
The current beiefly passes thru the contact, solder and wire end until the operator releases the foot switch, and then moves the tweezer tips to the next solder cup to repeat the process.
The tweezer tips only need to be kept clean (not tinned) so they can provide a good electrical connection with the contact or terminal to be soldered.
Te resistance soldering station provides a line/mains-isolated low voltage from a transformer that may have a variable duty cycle triac circuit, to adjust how fast the heat is generated in the contact. The variable duty cycle allows the operator to adjust/tune for different sized connections (very light duty for miniature contacts, or more sustained current cycles for heavy duty terminals).