Wire strippers were made precisely for this job. Places like Harbor Freight is where you can get them on the cheap. And I don't know what they're called, but there are razor knifes that are thinner than most which would work well too.
Wire strippers always got the job done for me as well. It is pretty straightforward to use. One just needs to be very careful to avoid cutting off more wires in the process. I got mine from a shop in my neighbourhood as they sold cheaper than what it is sold in Harbor Freight.
I agree that the wire strippers are the best for the job. I can't even think of a better option when it comes to removing wires from the coatings.