My customer today was concerned about me putting recessed lights in because the last guy came and knocked holes all over and pretty much destroyed the entire ceiling. I showed her the holesaw and dust bowl and the rest was history. Apparently the last guy did the same thing that you do, trying to cut them in by hand, and there were chips and straight edges outside the can EVERYWHERE. They looked horrible. This was just a plaster layer, so no wood/lathe to contend with, but it's the same result either way. Usually I wouldn't think much of it, and I really never take progress pictures on such a simple stupid job, but her concern made me think of this thread.
Anyway, 4 went in without a hitch, EXTREMELY brittle plaster...apparently. Of course I didn't notice because I didn't try cutting them in by hand. :happysad:
I kindly challenge you to cut a more perfect hole in to plaster, by hand.