Been doing this for 15 years of better. It adds extra nutrients to the plant and tomato itself. I've been told it's basically the same as miracle grow. I usually start putting it down at ground level by the stalk every 3-4 watering. I also believe it helps avoid the stem rot the tomatoes get now and then.
Pretty quiet here lately. Garden is doing good considering the heat. Going to need to pick some dill today. Cukes have lots of flowers and showing good signs of tomatoes too. Time to start adding Epson salt to the mater's.