Its only been a few years since I wrote my C of Q. What I did was purchase the Simplified versions of the Ontario Electrical code books both residential and commercial/industrial, and used the test questions at the back as a study guide.
The questions on the Actual C of Q are somewhat different, but this gave me a good idea of where to study and it gave me practice looking through the code book.
Like you, I did not pass the first time either so this is the approach I took when writing again.
Good Luck
