No matter what you do it will be real hard to clean the flavor out of the heads.
I ended up with a nice collection of attys, each with a different flavor, and a pages document that listed them along with what I had in them.
The best thing I found is clean the tank out and use a fresh coil. If you are switching back and forth between 2 flavors save the coils in a small bottle, medicine works great, and swap them back in when you use the flavor again.