When I went through CFS on the Bulldog in 1990, the course consisted of 6 weeks of groundschool. Then 27 weeks of flying, accumulating some 84 hours of flying. Graduates from the course were graded B2 and you were then monitored by your CFI flying with you about once per month, with another session in Standards after 6 months. Within the next 3 months you would be reassessed and normally upgraded to B1, which was 'average QFI' standard. After another 18 months, including a few more Standards visits, you would be encouraged to attempt an 'A2' upgrade. This required a fair bit of pre-course study, then 2 hard weeks at Standards flying about a dozen flights of 'A2 work-up' interspersed with theoretical knowledge and 'student' briefings. If deemed satisfactory (which was never guaranteed), you then went to CFS for Exam Wing assessment. This required a 'primary' teach, including a full 'student' brief, then the flight itself during which you would also need to demonstrate aeros before a 'secondary' teach. In my case it was 'Stalling 2', then 'Instrument Flying' and finally short-field grass landings. After that you had a quick debrief, then a long session of theoretical knowledge grilling. Your genial CFS 'trapper' would then, if you were lucky, advise you that you were to be recommended to Commandant CFS for award of the 'A2' (Above Average) QFI category...
'A1' QFIs were 'Exceptional' and very rare!
On leaving the unit at which you were teaching, if you were posted to instruct on something else, you started as 'C-to-I' (competent to instruct) before being assessed by Staneval for confirmation of QFI category on the new type.