well, the difference is that the edge will digg in slightly on the thumb, but not on your neck (or should not).
The skin on our thumbs are strong, and you should not ofcourse let it dig in that much, you will feel it when you try.
If you are afraid of razors, try another knife first, so you understand how it works, but remember. NO pressure..
This is equal to the TNT also, no pressure, wet nail, short drags.. you feel it quickly how it works.
And yes.. I was very scared of this myself, but, it worked fine.
But look on the above mentioned videos, he explains it and does it so you see how they do it. Watch it beeing done first, then it is easier to do it yourself.