If you've already started a course of treatment, stick to it, but just in case you're considering medication instead of salt, I've had very good luck so far with a malachite green + formalin combination med.
I had 5 < 2" clown loaches, and 5 tiger barbs in my quarantine tank when I got a really got deal on a 4" clown. I'm pretty sure the big guy brought the ich into the tank because the little loaches were in the QT for a week or two with no signs of infection.
Anyway, I already had the temperature up at 28 degrees celcius and had extra aeration going when I noticed the whitespot starting to take hold. I did a 50% water change and very thorough vacuum of the bottom of the QT. Then I added the half-strength dose of medication (as per the instructions).
After 48 hours, I did another vacuum + 50% WC and added the 1/2 dose of meds again. The ich seemed to be receeding. 72 hours later, I did the same vacuum + WC + medicate treatment again, even though there was no visible signs of ich. After another 3 days, I did another 50% water change to try to get any remaining meds out of the tank.
I didn't lose any fish during treatment, nor have I lost any in the 3 weeks since. Everyone is looking fat and happy, and in one more week they'll be going in the big tank.