I have a new, twice-seasoned (to 250C), (non-enameled) cast iron pan. Does the seasoning/coating remove the need to have it oven dried at the end of the day? Or it still has to be done no matter the seasoning?
If you use it every day or so, then no. There is no need to oven dry your cast iron pans once they have developed that dark coat. But after rinsing them you need to dry them promptly with a paper towel. Give them a barely-there coat of oil before storing. Soap is not recommended. The New York Times had an article on how to take care of your cast iron pan.
If your pan is new, the seasoning may not be complete. You will know you have a well seasoned pan when you can fry an egg on low heat and not have it stick. Until it is well seasoned, avoid cooking acid ingredients.
To season the pan use unsaturated fats (a vegetable oil like canola oil); they react with the iron better than the animal fats some instructions recommend. Because a seasoning pan smokes, I suggest doing it in the barbecue. Let it "cook" for 30 minutes with the temperature at 450˚F. Let it cool before handling.
Any exposed, non-coated part of a cast iron pan will be subject to rusting. Oven drying drives off the water before the reaction can happen to a noticeable amount.
The seemingly smart alec, but actually serious answer is: try to not oven dry it. If it does not generate rust, then it is seasoned enough. If it rusts, then rub again with light oil and oven dry. I tend to lightly wipe all over my cast iron a bunch of times until I get the entire pan nicely seasoned.