Don't use cast iron or aluminum containers to cook acidic dishes (e.g. vinegar or other acids). It will discolor the dish and discolor the pans. The acids reacts with the metal. Use stainless or porcelain for acidic dishes.
If it is not acidic, then cast iron is the best way to cook things that you need a pan for on the grill or smoker (e.g. baked beans, etc.).
Cast iron pans should be hand washed with mild detergent after use (don't leave them sitting around). Then dried in a warm oven. When dry, take a touch of oil and a paper towel and "re-season" the inside of the pan, and put beck into the warm oven for a few minutes.
Drying the pan and oiling it will keep it from rusting.
As far as the bacteria thing discussed, I cannot argue....
But for those of us old enough to remember, our mothers used to not scrub the cast iron really hard, because they wanted to leave the natural "seasoning" in the pan from the cooking process. The cast iron was clean, but certainly not spotless.
Just saying, I never had food poisoning....
Big Green Egg - medium
Cookshack model SM050
The Good One Rodeo clone