I forgot to comment on what I do now without the cool tool. Basically the same as JD describes. Score the outside, make a deep cut at the end, and tear away. It's definitely a job that requires a very sturdy and stable locked blade knife, and you can't be in a hurry.Truly an age old dilemma!
I don't like the cable strippers as the internal wires can be at an unpredictable depth and the stripper can nick it. The whole thing is more of an art than a science. For me, I score the outer casing with a box cutter, then score from that point down to the end of the cable. Next I rip the casing open starting at the end and up to the circular score, then tear that around. The whole concept is to not have the blade come in contact with any of the inside wires. (or thumb or forefinger!) When done right (say on 10/3 so) it only takes a couple of seconds. Fine for rubber, and plastic, but useless on Teflon or plenum grade cables! Still, there is a lot of opportunity for "box cutter" to become "thumb cutter" so what works for me might not work for you.
Like I said spend $20 on a good one and you'll love it. The good ones are precise and don't damage the wire. Quick and easy.gafftaper, yes, a rotary tool like that. I've used those ones pictured before too, including that exact model, did not like it. I think thats the some one that comes with the Coldheat (another waste of money).