re: How much grease do you normally skim from your C&S gumbo?

None. I used to but finally figured that out.

1) I don't do a 1:1 ratio with flour and oil. I use less oil than flour for my roux.

2) I brown my sausage and then let it drain well on paper towels. Pat it to squeeze out a bit more excess grease before adding to gumbo.

Those two things have done the trick for me.