You know, I have used corn gluten meal in the fall. It does help for some spring time weeds. In my area of North Texas there are so many weeds that it is a constant fight. I am afraid once it gets to be March, I revert back to something like Greenlight (chemicals) to get ahead of the really noxious weeds and then follow up in a couple of months with molasses for a litle fertilizer. I don't use much for fertilizer except top dressing with good compost and overseeding.
When I moved in, my yard was a hard, clay, baren patch where self respecting weeds wouldn't grow.. After carting in much compost, tilling, leveling, compacting the back yard, and two years of work, I finally have a nice stand of thick Bermuda grass. In the front yard, I have been top dressing every spring and overseeding. Aerations helps too. Worm casings are good for fertilizer but very expensive. The reason I say all this is because the theory is if you get a good stand of desirable, healthy grass, regardless of cultivar (St. Augustine or Bermuda), it will choke the weeds and naturally control the problems.