That's why you do multiples. The dog has to learn to move with you (not before you move

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I like to do it roughly half and half. That is I'll run the multiple as a multiple around half the time and break it up the other half.
Some trainers do a great job of training mixed. That is when they go to the line with a triple set up, they might do a single followed by double. I'll often do this and I also do three singles.
However, you still have to do the multiples, especially when you have birds that play off each other. I remember, Woody Thurman said at a retriever training seminar he was giving when I was a beginner, "Singles increase marking a little bit, doubles decrease marking a little bit." I probably butchered what he said but that was the general idea. I don't 100% agree with this but it's not entirely wrong either, depends on the dog and where he's at.