My technique for tutoring would focus on understanding the basics of each topic to begin with and then building on that knowledge using practice with past paper and other practice questions. This is because application is the key to understanding Maths at any level and practice is the key to securing top grades since being able to apply the theory to the situations you will be given in exams is what I believe to be the most important aspect of revision.
I have tutored GCSE students in year 10 before.
My latest Maths qualification has been my grade 9 at GCSE, and I have just completed my Maths A level and am awaiting results but I have been predicted an A* throughout the 2 years and my latest mock result was an A* at 91%.