I'm not sure what kind of
cast iron waffler you have, but I've made quite a lot of waffles in one of those small round ones with a ball opposite the handles to rotate it. With one of those, first you preheat both sides of the iron, then you pour the batter in and cook one side, then flip it and cook the other.
I would also use a good coat of clarified butter on both sides, after heating but right before adding the batter. Clarified butter is good for cooking because it has a high smoke point. So does coconut oil. As long as the waffles don't stick, you don't have to do anything to care for it, except maybe rinsing. The oil will build up a seasoning. If the waffles stick, it's hard to scrape out the waffle crust without also losing some of the seasoning.