There's a Kaplan book that also makes its way around med students, and I thought it was pretty decent.
The truth is, though, you kind of do have to work with a mnemonic to get through this test. If you think about it, the people grading you aren't medically inclined and won't really be able to pick up on anything subtle. You have to bash them over the head with your empathy hammer and make them know that you asked specific questions and looked for stuff on the physical exam. It's unnatural and isn't the way clinic is really run, but you're not really running a clinic. You're taking an exam.
You don't necessarily have to use THEIR mnemonic (I didn't). But you should create a system concise enough that you can write it quickly at the doorway, while complete enough where you are able to easily prompt yourself to ask all the questions you're expected to ask. It's nice in that you make all the patients somewhat the same, and helps make test day go by a whole lot smoother.
I can't speak much for your friend, since I haven't seen his score report or his performance. But I suspect that his failed performance might have to do with more than using a mnemonic.
