Rather than add study aids at this point, it’s more powerful to remove study detriments.
Turn off electronics and stop studying 30 minutes to an hour before bed, then get a fantastic night’s sleep. Sleep is when things get filed away in your noggin.
Limit video games/action movies that force the brain to focus on hyperactive stuff rather than processing learned information. The brain always chooses whatever’s moving fastest and loudest, that’s why commercials are so obnoxious–they’re trying to steal your attention.
Switch out 20 minutes of internet surfing with some sort of aerobic exercise, preferably outdoors. Not only does it reduce stress, it triggers a chemical cascade in the body that helps the brain make more connections faster.
Convince him to practice visualization by calling it VMBR (Visual Motor Behavior Rehearsal) and mentioning that Olympic athletes have been doing it successfully for decades. It’s as simple as closing your eyes and inventing a movie where you ace the frickin’ test. For it to work, you need to make it very, very real with details and emotions, like the smell of the exam room, the sound of the pencil scratching across the paper, and the overwhelming pride of being the first one to stand up, walk to the front of the room, and drop the exam book on the professor’s desk while everyone watches you enviously. Stuff like that.
I know this is really late, but maybe it can still help.