I was a Senior Trainer in the (Army) Reserves, before I retired. 'Public' speaking included 'hip-pocket' training (performed during any lull in daily activities) along with formal presentations, briefings and skills/leadership training. Army Trainers are taught to the standards of the IBSTPI. CompTIA's CTT+ (based on the Instructor competencies outlined by the IBSTPI) requires a 20-minute video of a training session. Powerpoint slides are a small part of training.