Before PowerPoint came along, some briefs were given on the dreaded OHP slide....
We were taught to turn the projector lamp off between slides, rather than change slides with the projector on. This ensured that students turned themselves off in sympathy and any with a knowledge of electrickery winced at the damage we caused to the projector bulbs.
Then there were the briefing slides themselves - covered in strips of card hinged with tape, which we were required to flip over with a knitting needle or similar. Of course if this was in response to the answer elicited from the student, there was always the risk that he/she would provide a logical alternative which wasn't on the slide.....
I hated the wretched things. A white board (and 4 colour dri-markers) was so much easier and less distracting.
At one RAF base, the grumpy station commander growled at one briefer for using his finger rather than a pointer to highlight the topic to which he was referring on the slide. So he made himself a large arrow from cardboard. The next day he started his brief and placed the arrow on the slide. The whole place erupted, because his skill with scissors and cardboard wasn't too good and it looked for all the world as though he'd just flopped his....male appendage onto the slide. The station commander was even less amused.....
I once had to give a met brief using an OHP slide. As the audience included a certain rather unpleasant station commander, I took a lot of time and lovingly coloured the cold front in blue and the warm in red, with black isobars. It looked very smart indeed. Then I switched the projector on and was aghast to see no trace of colour on the screen. "Sorry, sir - I should have checked first. It's an old RAF black and white projector", I announced. The station commander's eyes narrowed to slits.
I learned about chingraphs from that - their wax is opaque.
At a different base, the met man was just about to kick off his briefing when a rather more jovial station commander called "Morning, MetO - have some actual!" and lobbed a snowball at the met man. Which hit him on the chest, then fell onto his slides.....which he'd prepared with water-based lumocolour pens - and the whole picture turned into a multi-coloured splodge. That didn't put him off though, as he announced "As you can see, we have a very confused synoptic situation - with low cloud and snow all day".
PowerPoint has its place for certain applications (e.g. the theory of stalling - perhaps), but I agree that it is quite inappropriate for pre-flight student briefs on how the stalling exercise itself will be conducted.