I use Ideal brand wirenuts which require no pre-twisting. I use a Wirenut "wrench" (mines not built into my screwdriver, but a similar tool made by Ideal) and tighten the wirenut "almost" to the point that it splits, if you remove the wirenut, the wires will be twisted together, just like the pre-twisted ones! I defy anyone to tell the difference between whether I have pre-twisted or not, if they haven't seen me install the wirenut.
I agree with Tom, pre-twisting is a waste of time when the end result is the same... or maybe it's just a WV thing, I don't know...
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