How to solder micro stepper motor pins?

I would probably use a small amount of tacky flux and pre-tin both the wire and the pins.

If you can secure the motor in a clamp with pins facing horizontally, that would be ideal for me (an average solderer).

I would feed the wire with my non dominant hand while resting my palm on the bench top and soldering with my dominant hand.

Hope that makes sense. Pre-tinning will make it relatively easy.

The pins on each motor seem to be all in a single plane; perhaps you could make a custom circuit board that fits those pins and functions as a breakout board.