This is what I have been using, heck I even take a big chug now and then. I also have soaked grates in a mix of 50/50 white vinegar and water over night for the rust. After rinsing and drying I put on a light coat of this stuff, wipe any excess off, less is better than more. If it will fit in you house oven bake it about an hour at 350/400. Repeat if need be. Have not tried bludawg's method but I think that would work as well.
Side note, cooked some chicken breast in a 500 degree oven in a pre heated cast iron pan last night, with nothing but the chicken, it looked better than ever when I cleaned it up later.
I would not coat it with flax before or after each cook it would be cost prohibitive, instead use cheap veg oil, but I have some good coconut oil, and may try, it has a very high smoke point.
After saying all that, I think if you just wire brush it, and wipe it down before cooking it will be fine, just except that it will rust a bit between cooks, but it certainly will not effect you or your food.