I dont the as much time as you in the back, only about 2000hrs in the back of a blackhawk, and I was a crew instructor for 6 years. I've been there and helped with instrument training from the back. I just finished my instrument back in October. The knowledge part was no big deal, as with you. The theory of instrument flight, all made perfect sense, in practice was the hard part. keeping the thing greasy side down gets tough as the CFI changes things and fails things.
I used the jep prep book for the test, because the school made us buy it. It's ok, (note the little ok). I bought the dauntless IFR prep app for my tablet and liked that much more.
I highly recommend this.
http://www.amazon.com/Pilots-Handbook-F ... t+handbookthe IFR section, which is 3/4 of the book, is written in the phase of flight as it happens in order, and what info applies to that phase, and how to apply it. makes it really easy to read and understand.
My friend let me borrow his Rod machado's IFR manual. I had to force myself through two chapters, and couldn't handle it anymore. just full of blah blah. 98% of the book I'm sure is jokes. I cant back that statement up though because I never could force myself to read it. I'm sure his books have helped millions. Hes been a famous CFI for ages.
good luck