I've seen it suggested that 2lbs per surface acre be added annually. I use this formula and have been for several years. It seems to work ok. However, like most forage, if you can afford more then it won't hurt anything. As for hay, I don't use it. I have lots of cattails and I release the crawfish from the boat along the outer edge.
I'm hoping that the crawfish take cover and bury up inside the cattails.