The only difference between the WA Admin and Masters exam is the number of calculation questions.
If you go to the L&I electrical section web site, then under exams, find the exam content information, and you can see the number of questions for admin and masters
By the way its an open book exam and you can take any trademarked book into the exam with you.
Not many have taken the masters exam, just a few in Jan 07, but those who did had high passing scores, probably motivated to pass.
The CITC prep class should be fine. You may do as well with the Mike Holt exam prep material.
You need to be very, very good at calculations.