How can I get salt to stick better to buttered or oiled popcorn?
The key is to have the finest possible salt. One way to do this is to take any salt you like, and grind it fine in a mortar and pestle. This just takes a few seconds, and then you can customize to a particular sea salt you enjoy and avoid the need to buy a special popcorn salt. A rotating action in the mortar and pestle (as opposed to pounding) is most efficient for grinding salt.