I'll chime in as someone who used First Aid for the USMLE and used the Dental Decks for NBDE. They are both tailored to 2 completely different exams. I don't think First Aid would be helpful for NBDE. The dental decks are released test questions put onto note cards. That's all I used and it got me a 92 on the NBDE. But that was about 7 years ago also, I'm not sure if things have changed since then. Likewise, the dental decks wouldn't be much help for the USMLE.
