PRO TIP:

If you're unable to find fine salt, and the only coarse salt you can find has a plastic grinder inside the bottle (HORRIBLE, because it grinds microplastics straight into your food...)

It's actually SUPER EASY to crush coarse salt down into more of a powder.

Just grab a flat surface (wooden cutting board, even a plate works) and a curved surface (like the cup I used here), and go to town.

A few little pieces might fling off onto the floor, but overall, it works quite well.