be careful of too much heat

use a second DB connector to help take a bit of the heat and to keep the pins in alignment.

be quick with the iron and you will leave a clean wet joint
don't move while the solder " goes off "

as I said ... don't stay on the pin too long cause you will melt the white plastic

I try to use silicon tubing to cover the solder joints and if things get tight I tube every second pin

Use one of those multi-angle mini-vices to hold the connector at the best angle for working at. Position the vice so the weight of cables as you connect them doesn't pull it over. If you have a multicore to connect, pry apart the strands of each shield about 3/8" from the cut end and feed the insulated core through the pry hole. Twist the shield into a pigtail and trim 1/8" off the core insulation. Repeat for each of the multicores. Check for rogue strands of the shield braid.

If the backshell is the type you have to feed the cable through, do that now!

Use solder to tin the solder buckets on the connector and also the bare ends of the multicore (both pigtail and core) taking care not to melt the core insulation or the plastic holding the connector pins. Carefully solder the wire pairs to the socket pins in turn, doing core then ground pigtail. Before soldering the grounds, slide heatshinks over the pigtails if you have any. Heat the socket solder bucket enough for the wire to slide into place.

Contunue attaching wires, turning the angle of the vice as you go to maintain access to the next bucket pair without catching the iron on the cores already connected.

After all the wires are connected, inspect the joints, giving each one a slight tug. Check clearances and also look for stray strands from the pigtail causing shorts. Shrink the sleeves and fit the backshell. Job done!

If you aren't in a situation where cables are constantly going to be plugged in and unplugged, I'd go for the easy route and use the crimping pins and crimping tool. You'll still get a good connection and it takes a fraction of the time. Crip your wires, drop the pins in, use shrink tubing to strain-relief and clamp the shell on... Done in a pretty short amount of time with a reliable short-free connector.

--Ben

High heat will allow you to solder quickly, not having to leave the tip on long.
A Weller soldering station with an 800F degree pin tip, is my weapon pf choice.

Too low of heat and you will spend too much time making a good solder, and will melt the pin insulator.