In addition to the medication, you should also slowly raise the temperature of your water to 85 degrees. You can do this over the course of several days. As long as you have adequate water movement to keep the water oxygenated, the fish won't mind the higher temperature. I'm not sure if the medication you're using contains any salt, but if it doesn't, you could also add aquarium salt to the tank.
Also, never flush a fish, live or dead! I don't understand why people think that flushing a live fish is a humane way to euthanize it. Willow mentioned the reason why you shouldn't flush a dead one, either. If any of my fish die, I usually bury it in the yard where it can act as fertilizer.
Here's a thread about ways to humanely euthanize your fish:
http://www.fishforum.com/viewtopic.php?t=943
However, I do not believe you need to euthanize your danio, as ich is definitely treatable and has already been introduced to your aquarium.