First, some quick numbers. 21 people came (plus the child of a participant, who was playing video game). 17 people remained up to the end of the workshop. I asked what was their experience with anki. 4 of them used it regularly and wanted advanced tricks. A third already tried anki but had given up. The remaining never used anki.
A little bit of context. I had the idea of this workshop during the 2nd day of congress, after having seen a lecture «introduction to vim». I realized that there is a free software I use a lot, and that I can make a similar introduction, and furthermore that I probably can't make it worse than the vim introduction. Planning a workshop during the congress is usual for C3. After all, it's a chaotic event. However, it means I had little time to prepare myself. I had something like 30 hours, during which I had to sleep twice, and also to enjoy the congress. I missed my train and arrived to the congress 1 hour after the planified time of my workshop. A friend put a message in the workshop room stating that the workshop would be 2 hours later and in another room. But it problably means that I lost a part of the people wanting to attend. Especially since the workshop was given at the same time than the closing event.
Since some people already know anki, if I decide to come back next year to 3C, I'll do an introduction, and an advanced talk. I think separating both will lead to better content for everyone. I may even due the advanced talk twice in 2019, since I intended to do it in a yearly rationalist event in september anyway.
My main goal was that the workshop would actually be a workshop. I wanted them to practice, by doing basic anki stuff. I didn't actually checked whether they were doing it, so it's hard to state whether they did succeed in it. To be more precise, the only case in which I was sure someone was actually trying is if those people had a problem using anki. This was the case, in particular, of someone who did download the deck «multiplication table» on https://ankiweb.net/shared/info/1680286867 . This person wanted to understand why the first seen card was not 2*2. I first thought the deck's option was «show new cards in random order», but instead, it is because the deck was shuffled before being exported (according to ord number at least). I realized afterwhile that spending even 3 minutes on this in a 50 minutes workshop is a real bad idea.
Since I wanted this to be a workshop, I didn't want to spend a lot of time on content which can be found in articles. And I have to thanks anki's subreddit and anki's discord channel for giving me a lot of articles. Instead, I listed those articles to them and stated what kind of content they may expect to find in those articles. Letting them note the title/url. I didn't even have the time to (re)read all of those documents again.
One question I had was about motivation and time. How to find them. I must confess that, while ankidroid helps by allowing to review anywhere, I didn't really have any answer for this. I guess that what I should have stated is that I actually see the great improvement it made to my life, so it helps.
Speaking of improvements, I showed them four examples of cards. In four domains in which I improved. Guitar: by showing a piece of guitar with a part missing. This allow me to concentrate on the part I actually need to practice, and not on the part I already know. A face, where the card ask for the name. A method from the Python's library BeautifulSoup. And a card about a combinatoric sequence.
I explained that one great thing with anki is that it can be used differently for different kind of knowledge. And that I can use it to learn deep mathematical facts in a way which is quite different from the way one would learn vocabulary. I used the example of the square. A square is a rectangle with two adjacent side of the same length. A rectangle is a parallelogram with a right angle. Thus, in order to learn what a square is, you must first understand rectangles, and before that, parallelogram and right angles. (This is actually a bad way to give an intuition of what a rectange is. But this is a concept which is easy to follow for non mathematician). So the fact that anki allows to see new card in a particular order ensure that I'll still learn thing in an order which makes sens. Furthermore, even if I have problem with geometry and don't feel like I'm ready to learn what a square is, I can use multiple deck to separate geometry from multiplication table. Thus I can learn multiplication tables quicks if it's easy for me, while I still go slow on geometry. (This may be why someone did download the multiplication table deck).
I also use the example of «monade» which is defined as as «a monoid in the category of endofunctor». I explained that anki may let them learn this definition by heart, but it won't help them understand it if they don't try to first learn what monoid, category and endofunctor means.
I wanted to show anki without and with add-ons. But I forgot to start it while pressing shift, thus add-on loaded. Since I use the add-on https://ankiweb.net/shared/info/877182321 (enhance main window) the main window was actually quite more complicated than it needed to be. I hope it didn't scare anyone. I stated that if anyone wanted to hack an add-on, they could contact me. I'd probably be a good introduction point. But no one seemed interested. Someone wanted an add-on, but not to create it themselves. I'll do this add-on if they indeed contact me. I must admit I'm a little bit disapointed, but not exactly surprised.
 I wish no disrespect. But seeing someone using vim is not really interesting, even when the pressed key are shown on screen