As part of the regular care for a cast iron pan, I regularly leave it empty on the hot burner until it smokes, which I understand to be libun gamur. Since I am not doing this for the sake of switching the kli from meat to milk, can I swap it back and forth after it undergoes this process?
Not on a regular basis.
If I cook meat in it, then bring it to smoking, can I treat it as I would an aino ben yomo?
This would kosher the pan and render it pareve. However this shouldn’t be done on a regular basis to switch between milk amd meat.
It was my understanding that a seasoned cast iron cooking ware does not have to be kasherized. It is enough to immerse it in a Mikvah. However, I think it was suggested to have separate dairy and fleischig pans. Maybe I misunderstood, but my impression was that you cannot interchange dairy and fleischig cast iron pans?.
You are correct. They shouldn’t be interchanged on a regular basis. If one decides to change from meat to dairy or vice versa, that’s ok.