My usual method is just to brute-force linear scan from left to right, top-to-bottom. May not be elegant, but it works.
I, on the other hand, 37 years later,am basically permanently crosseyed from the experience lol. It somehow became a resting state for me from all of the practice, so I’m always doing it on any kind of repetitive patterns, and even “successfully” on random ones which does some really weird stuff in your visual cortex.
As it happens, I also can't focus on the images in TFA after crossing my eyes to get the shimmer the author refers to.
In my recent years I have developed some astigmatism, but I can still do them without difficulty.
Makes you wonder if the kid he was talking about had a lazy eye or crossed eyes or something.