You're gonna hear alot of scary stories about Insulin... kind of like stories told of the HORRIBLE sides of Tren.
Not discounting its dangers, just saying, like anything, if used properly, and under proper care, it is the most anabolic thing out there besides food.
With that being said, Slin is not used for cutting in the sense that you are asking. I have seen it used during show preps, but that is under the care of a nutritionist who knows how to use it and the benefits/dangers involved. Also, and most importantly, Slin doesn't discriminate. It will transport everything to the muscles, including fat, this is why most people get it wrong. 200g of carbs can turn into a mess if not timed properly.
I used it off and on a few times with high doses of GH with great results, but even checking blood glucose and getting my timing dead on, i still went hypo a few times and it ain't any fun. I wouldn't suggest, and don't offer ways to do it, to anyone unless i know them and they really need it. I could almost bet you don't.
Hope this helps more than the typical 'scare tactics' without any explanation other than "you could die".