The "teaching skills" bit of my FI course was fairly basic and old fashionned. Teaching techniques have moved on, and indeed variation in techniques using different environments for specific objectives increases effectiveness. For Ex 3 I nearly always brief at the aircraft, whilst doing my external checks. This seems to me to be the correct environment for this brief for most people. The content and is taylored to the individual. It might be interesting for the HoT who insists on the use of white board to justify his/her stance on educational grounds. A short audit of information recall using comparing white board and A/C briefings might be valuable.
What has not been mentionned much is the position of "accompnying persons" in the back on Ex 3. Our CFI has tried to get a sensible answer about this from the CAA, but they will not commit themselves. Arguably the person in the back is also getting "Air Experience". In reality, I frequently shared an A/C with another student when doing the CPL and found sitting in the back observing another student immensly beneficial. Doubt whether it was strictly legal though!