You have to set your mouth just right.
Usually, I cut into the outer jacket right next to the equipment ground & run along it to the length I want plus a couple of inches. Then I pull the ground out, next I strip some jacket of of the single conductor & then I can usually pull it through the thin area in the jacket that used to separate it from the ground. Repeat the same trick with the remaining conductors & do some careful trimming with your knife where you want the jacket to end.
Of course, a propane torch is much faster.