I have a frozen Butterball injected with a saline solution. I don't want it to be too salty.
I don't think you should dry brine a turkey that has already been injected with a saline solution. It has, essentially, already been brined.
My instinct is to agree with Susan W and it seems like I read that somewhere - however when I looked at the comments about the Judy bird on the Food 52 site Frank seems to be the expert and he says you can do it.
It's Serious Eats and I thought Russ Parsons that says not to brine a kosher or injected bird, but maybe Frank is on to something.