At least with the people i've helped do keto, I find doing a initial over feeding of whole keto food is very beneficial in fighting the initial cravings and adaptation phase.
Huh, interesting. I've generally heard the recommendation of fasting beforehand instead.
Personally, I suspect the quickest way to switch is to do intense exercise between the last non-keto meal and the first keto meal. It'd burn through a lot of the glucose glycogen stored in the liver and muscles, forcing the liver to release ketones immediately instead of waiting a day for them to deplete normally. Though you'd probably get the shakes from hypoglycemia in the meantime.
For me, I've just switched to keto foods and let the switch happen on it's own over the course of a few hours. No need to rush it. Thankfully I have a harder time going off of keto than getting on