I like aquarium salt as well, it works for a bunch of different illnesses! :) But I keep medicine around just in case :)
I have used Walmart's QuickCure if you want to get it as backup. Use the tetra dosage though! :)
I wouldn't trust that Ick Guard you linked, I don't see how you could kill Ich without raising the water temperature while not harming your fish. It would have to damage the fish's slime coat or something crazy... and Ich cannot be killed while attached to the fish. You have to raise the temperature to make it unattached...
This is the one I used: http://www.walmart.com/ip/Aquarium-P...fl-oz/10313376
I would still try to treat with salt first, and only use this if he doesn't show any signs of improvement.
QuickCure is pretty hardcore stuff, it will kill EVERYTHING in your tank and dye your tank temporarily blue... I only used it for 3 days since it's so strong.