Depending on what fish you have, using salt as well as heat will have additional benefits.
Research and make sure your fish aren't sensitive to salt.
Raise the temp. about 1 degree every 6-10 hours until you're around 86F.
Add salt as directed on box (if fish are safe), do a %50 water change after week 1, re-add the salt with temperature matched treated tap water. Add some stress relief/ slime coat healer during this PWC, but not a full dose.
Keep heat up for another week, and see if ich is still present. Can even keep heat up for an additional week to ensure the ich has subsided. Slowly reduce heat the same way you raised it.
I successfully treated neon tetras and cardinals with the heat and salt treatment, while tetras are sensitive to salt.