When you need to split a thread from 6 strands to 3.
Start in the middle.
I find this is the easiest way.
I cut my threads about 18" long, then gently tease apart the threads at about the middle and slowly pull apart.
It will twist and turn as you go. If it stops parting then hold the closest end with your teeth to put some tension on and continue to pull apart.
Then hold each section up by one end and it will untwist as you run your fingers down the thread.
This is the method I use. Hope this little tip is helpful
Happy Splitting and Untwisting