The technique with the markings on the edge of the card is also used in a well known card magic routine - but using wax instead of infrared ink, so you can feel

The technique with the markings on the edge of the card is also used in a well known card magic routine - but using wax instead of infrared ink, so you can feel the slight differences in texture when you handle the card (though only if you're paying attention to it). Takes quite a bit of practice, though.