There was a kid at my school who wrote on both sides, on top of eachother with both red and blue pens. He then brought in red/blue 3d glasses, and would close one eye to filter out red/blue and read the notes.
Half my engineering exams were open book. If you did know the material you generally didn't have time to actually look it up so didnt matter.
I had an elective class that was open notes/book so I collected all the notes and resources the professor provided, put them into a single PDF, and then just text-searched them in the class. Worked well but the class was a joke and it didn't matter if I left knowing any of the material. Just had to check the box.