Hey IcarusFlyby,
If you mean the “aviation connectors” on the cheap no-name or Huanyang spindle/VFD kits, it’s also difficult with two good eyes. Those connectors are not motor power connectors. I would better avoid soldering a spindle cable at all. Professional spindle power cables are crimped, not soldered.
PS:
Frankenstein Bench → Hardest part is soldering Spindle Connection
Are you really omitting shielding?