Swim Bladder help

Three days ago I posted about my betta having suspected swim bladder, well I fasted him for 3 days and maintained water temp and see little to no improvement. Today I am setting up a hospital tank using water from an established tank, and his current sponge filter. how much aquarium salt should i add? how long should i wait to add him in? should i used a substrate like sand? or no substrate and keep the bottom bare?