I studied for an entire summer to take the initial CFI checkride. I work 9-5 but studied in the evenings and on the weekends. It is one heck of a big checkride. You need to make lesson plans for everything in the PTS for PVT and COMM. My best suggestion - work on it full time over the summer when you aren't teaching and you'll knock it out in a couple months. Use a local FBO and do the 'slow & steady' method. You'll be a much better CFI because of it and benefit your students much more. When it came down to my checkride I whizzed through it and even got an email from the FSDO Examiner the next day telling me how nicely I did on my ride. I knocked out the MEI & CFI-I in 3 weeks working part-time at it in the month after my initial ride.