My first clinical instructor utilized techniques from Maitland, McKenzie, and Mulligan. He saw significant results with his patients. I am still in my second year of PT school so I have not completed any of the certification courses but plan on doing at least the "first level" asap after graduation. Just like anything in PT you can lose yourself in a single technique if you don't keep your wits about you. Remember, Maslow's statement "if all you have is a hammer, everything looks like a nail"?
Maitland and McKenzie are great models of how to perform a precise physical exam without the use of imaging and how to track/progress a patient's progress. Maitland and Mulligan are manual based treatments. There is some overlap between all 3 of them but it is difficult to decide what is the most effective because there is not a lot of research that says one is "better" than the other and therapists tend to lose themselves in one or the other. They are all legit approaches though. In my mind they are what make PTs just as good at treating joints as chiropractors. I am sure your CI just needs you to understand the basics (your first year biomechanics/anatomy as well as what you can find on the topics from physio-pedia etc. ) and will share with you more in depth info and resources at the site. My CI had loads of books and materials from training that he had attended that he had me look through. Don't be afraid to ask for that stuff while there- most PTs keep those binders and continuing ed materials at their desk and in my experience are always willing to share! Good luck to you!