Here is a technique I have had good results with.
Warning-----you need extra length to do this, dont cut wire to size first.
I just get the outer sheath cut open however I can, strip off 2-3".
Then grab one of the wires, and use it to tear through the outer covering, (pulling it back away from the cut end) down as far as needed. Lastly, trim off the excess outer layer.
The advantage here is that no cutting tool has a chance to nick the tiny wires inside------yes, you will waste a few inches, but that is a price I am willing to pay.
Try it on some scrap first, to get the hang of it.
Remember the old oatmeal boxes you opened with a string, or china pencils???? Same idea.