What do you mean "feeling"? What do you mean "self taught"?

If you looked at the application, you would see that it asks for information from virtually your entire career. The IAAI-CFI certification, as well as CFEI are not designed to be a piece of paper you study for for 4 hours and then sit for a test. Its not supposed to be easy. If they were easy to obtain, they would have no value.

While each question is tied to a specific source, succesful completion requires a body of knowledge acquired by an experienced fire investigator over the course of a career.

There are hundreds of questions in the test bank. Each exam is randomly generated. So, while the proprtion of questions on each subject remains constant, the exact questions will never be the same.

Its your career. Its your certification. The road to that certification means you get the books, develop a study plan, stick to it and take the exam. I don't mean to sound so blunt, but there really is only one way to do this.