We don't measure, but here's how we make it:
Make a cornbread and let it cool completely, maybe even overnight. Once it's good and cool and firm, break it apart into medium/large pieces (it will crumble more as you handle it/mix it) and lay out to dry. The drying time depends on how moist you cornbread is, but give it at least half a day.
Melt a bunch of butter in a frying pan and saute in it: chopped yellow onion, chopped celery, chopped fresh sage (lots of it) add salt and black pepper to taste and toss together with cornbread. Bake until hot through and browning on top.
We are gluten-free, so our all-corn cornbread is quite crumbly. If you use some wheat flour in your cornbread recipe you will have a little more leeway with crumbling.