This is from a dear friend who racked up tons of experience (long ago) as a regular at the golden arches.
“When you order french fries, tell them you want them without salt.
“This way, they have to make them fresh rather than give you ones that have been laying around for a while.
“Then you can just slyly sprinkle them with some salt you brought with you.”
Better yet, that’s the point where I would look them straight in the eye and say, “OK, do you have any salt?”