I've taken that dang Instrument written 3 times (Instrument, IGI, CFII). The best thing that I've found to work for me was a combination of the book and Gleim software (school has that for free).
I'd start by going through the book, page by page, quizzing myself on all of the questions using the answer hiding sheet in the back. If I got it right, I'd leave it alone. If I got it wrong, I'd circle it so I'd know as to come back. If I was unsure, I'd make a note and come back to it as well. I did this with the entire book, cover to cover. Then I went back through all of the questions I didn't know and analyzed why I got it wrong and tried to find some memorization items or thought mechanisms on how to remember or learn what the answer was.
After re-covering the book for all the answers I missed, I ground out a few days on the Gleim software in Sample Test mode exactly as it would be on the real test. We have LaserGrade here so I used that emulator. That made the transition into the actual test somewhat easier because it looked the same. Plus by the time I had that done the only thing I saw was that damn ugly blue background.
I took practice tests until I was satisfied with myself. This was usually when I was continuously getting 95+ on the practice tests. After about 5 of these, I'd go take the actual written. I can proudly say I've never gotten below a 93 on ANY of my writtens thus far. Private, Instrument, Commercial, FOI, AGI, IGI, CFI, CFII.
As an instructor, I can't stand students that don't study for their writtens. That's a huge pet peeve I have. I figure, within reason, that if I could do it, so can you. Depending on the student and his/her willingness to learn, I usually ask for 3 90s or above on practice tests before I'd sign someone off for a written. No BS, just bring it to me so that I can see the finished copies.