Study Suggestions for National Asthma Educator test?

Hi y'all: I am looking for any advice on reviewing or studying up for the Asthma Educator - Certified exam. After reviewing the matrices of materials covered in the candidate handbook, I am wondering where to even begin.
Has anyone purchased Kettering's home study review? Is it worth it? Suggestions for other reviews?

Thanks
I was wondering the same thing too. Where to start?