Depends on the EC5 bullets and tubes. Some have a chamfered end where they slid into the bottom of the EC5 blue shell, while some have the chamfer the other way and the wires need to be through the connector first before soldering.
That being said, the best suggestion I have for the connectors that are soldered through the blue housing first, is to take one spare male connector with the tubes, one spare female connector with the bullets and press them together, using a vice, channel lock pliers etc. After they’ve been pressed together, you now have two fully seated connectors. When you’re done making the solder joints on a female connector, grab your premade male connector and use that to seat the female bullets in the housing and vice versa for the other ends.
Hopefully that makes sense!
Edit: I use heat shrink on the ends of the brass connection points to cover the solder and when finished, provides a good seal between the connector and the EC5 housing.