Any salt will do, though you can get slightly different effects from the different kinds. Making it work is a little tricky and I still don’t get it right every time.
The salt effect occurs because it soaks up some of the moisture, leaving hard edges and light areas.
If you add the salt too soon, it just all melts away. Too late and it doesn’t soak up enough moisture to make a difference. So you have to learn when to add the salt. Obviously drying times matter, so some papers don’t work well because the paint dries too fast for you to get the salt down. Changes in humidity can mean you might have to wait longer or add sooner. Essentially, you have to learn what the look is for the right time to add.
You need to start with quite a bit of water, the paint should be wet enough to move around, though it doesn’t need to be drippy. Then you let it dry to the point where the paint doesn’t move easily, but there is still a shine to it. That’s when you want to add the salt.
I practice by painting blocks of color on the paper I’m using, and adding salt at different times.