re: Gumbo turned out greasy and watery

once thawed, let it sit out or in the fridge the fat and grease will be much easier to skin than when simmering.

To thicken, maybe a tablespoon or two of jarred roux and cook through for 30 minutes?

When I store any kind of stew, chili or gumbo in the fridge after cooking, I usually put the entire cooking vessel in and leave it uncovered. This helps the food cool at a faster pace, allows for easier skimming of the fat the next day, and seems to thicken everything up a bit more.