I will say that it is very important to get all of the kinks out of the individual wires. I found that curling the wire over my finger and running my finger to the end of the wire (like you would create a curl on a gift box ribbon) takes the kinks out (effectively reproducing the way TigerWillow1 does it - just using my finger instead of a tool). Do this on each "side" of the wire (so four times on each wire) and you'll get all the kinks out. That makes it MUCH easier to push the wires through the connector. If there is even a small kink in the wire, the won't push through because the space tolerances are so tight.
Same reason I do it, just a different technique
here, excerpt below:
I have even better luck by using the non-serrated, flat part of my needle nosed pliers to gently flatten the wires, one at a time, in one plane then rotate the pliers 90 degrees and flatten in another plane. They then lay closer to each other, go into the insert easier, and allow the insert to get closer to the outer jacket, all the way up to where each pair's twist begins.
