Many people recommend break in rope by rubbing it against itself. This is not something I recommend as it damages the rope and makes it more likely that you will break your rope.
How people break rope
The method people recommend is is placing a rope over a carabiner, ring, or piece of bamboo then twisting the rope so that one rope is wrapped around another, and then pulling the rope back and forth to soften it.
This means that the rope is rubbing against itself like sandpaper.
If you try this on a small piece of scrap rope you will see that as you pull the rope back and forth rope fibres will come of the rope and it will thin. The picture below shows two half's of the same rope which hasn't been treated with rope paste .
Rope paste and oils help protect ropes from just this kind of friction, you really don't want to be artificially creating situations in which your rope is being placed under unnecessary friction. . The one on the right has been repeatedly broken on the same spot - as you can see the lay has become a lot loser and the rope has become thinner. 
The thickness of the rope before it was broken was 6mm:
After repeatedly breaking the rope it is 4.36mm!!
