It IS the same principle, essentially. Personally, I feel needle and thread method [or in my case needle and dental floss] is a little safer with dolls because the plastic is SO soft, and the holes so close together in some areas, that with ar ehairing tool you might risk ripping plugs, especially if you aren't familiar with doll heads enough to know the amount of pressure to apply. And honestly? I'm not sure about ken, but any doll I've deheaded, I've gotten a firm grasp on it with one hand, and another on it's body, and with slow even and unrelenting pressure I've pulled them apart [keep your hands even and straight so both the head and doll are still in allignment while you are doing this and you aren't accidentally angling it to one side or the other which may cause a bend or break] But I do this VERY slowly, because if you are going to have an issue you can usually feel it coming. But I don't usually have problems
But yeah, it's pretty much as time consuming as doing a pony, except in some cases more so! hehe.