In a skillet over medium high heat sauté onion, celery and green onion with butter for 5 minutes, until softened. To the skillet add sage, 2 tsp thyme poultry seasoning, garlic salt, pepper and granulated garlic.
In a large mixing bowl, whisk together eggs, soup and 3 cups broth. Add cooked vegetables, cornbread and bread to the bowl. Mix until fully moistened. (Depending on the dryness of the breads, add additional 1 cup broth. The mixture should be fairly wet.)
Spray a 6 quart slow cooker or similar with cooking spray. Pour dressing evenly into slow cooker.
Cover opening of slow cooker with doubled paper towels then place lid firmly on top. (This will prevent condensation from dripping back into the dressing.)
Cook on high for 2 ½ -3 hours or on low for 4-6. Uncover and let stand for 5 minutes.
Garnish with reserved thyme and additional sage leaves before serving, if desired.