When it comes to solving the mystery of visualizing unseen hands, World Champion Mike Lawrence’s books and software provide the best guidance I have encountered. Here is Mike’s website: http://michaelslawrence.com/
Here is a fine example one of his books:
http://michaelslawrence.com/product/how-to-read-your-opponents-cards/
I benefited immensely from this software back in the late 90s: http://michaelslawrence.com/product/counting-at-bridge-2-cd-for-pc-only/
Mike gives us daily puzzles to help improve our game. Go to his BridgeClues site: https://www.bridgeclues2.com/ to enjoy and learn.