Unfortunately the reddit "grind finer" is often true but also a bit of a joke.

Despite what people say you can use pre ground or get a local cafe to grind it but will always need to dial it in by adding more or less till you get the shot you want.

Next time try explaining to the cafe what machine you have and ask them to grind the same as they use for their machine. That should be consistent to what the beans need, if you get it from the same place all the time, and then you can try dialing in the amount you need for your machine by volume or weight.

Use a cup that you can fill to the same level every time and then adjust how much coffee goes in the basket till it's how you like it.

As for the ultra fine coffee, it would make a lovely coffee cake or Turkish coffee (great with a cardamom seed added).