The commercial standard seems to be the Ideal strippers. They're accurate and won't nick the strands if used properly. When new, they do well with Teflon insulation, though a thermal stripper is the cats pajamas for that. Though some despise them, sometimes I like the automatic strippers. The best ones don't have blades like the Ideal, but a sort of wide piece of metal where the cutting edge is in the center. They're only for freehand use and don't get into tight spots at all. I'll go out on a limb and suggest that any manual method using knifes and such will leave at least microscopic nicks on the strands that are highly undesirable. You'll fail your wiring and soldering course if any nicks are present!
I've always wanted an automatic stripper for hard enameled wire, but those come a bit dear. They usually have orbiting and spinning abrasive drums.