Crock pots are great because they don't get too hot. The water method is how I was instructed to make butter. They said 4 to 8 hours but recommended 6. That said, I don't think that using vaped week is going to result in much if anything in the way of medible. All the canabinoids and THC are spent during the vaporization. My guess is you will just end up with some nasty green butter.