I am studying now for the CMQ/OE exam, and I am actually looking for a study group/partner to join my effort. Anyone?
I was not able to use this approach, maybe it would work for you but I suggest you invest in a bank of test questions. I found the ASQ versions were superior to those from QCI and found I retained information much better when looking up answers to questions than if I just read the books.
As for reference books, many are used to write the exam questions but I only brought three into the examination. Many years ago I was on the editing team for three Certified Quality Inspector exams, and found (whether they meant it that way or not, I do not know) the ASQ Handbook for that subject was the best source: it most accurately matched the largest number of questions as opposed to other sources.
I hope this helps.
Disclaimer: I am an ASQ member.