If your in keto your blood sugar is likely to be low, adding insulin may result in serious hypoglycemia. Tread carefully if you decide to do this, but I would not recommend it.
Yes I've used to to get into ketosis faster and also used it while in ketosis (most people should not attempt this) pre workout not a big dose and not a lot of carbs. I enjoyed it a lot cause I never felt bloated and distended from the slin since I was in ketosis for most the day.
Also I've found Metformin a few times a day was better for speeding entry into ketosis than insulin which is odd.
X2 on this. I wouldn't attempt the slin route unless you really know your body and how it reacts to low or no carbs in certain doses. Go the Metformin route, much much safer!