You may have already picked up on this one. I found its a link from the Ray Jardine site.
I know a couple of guys who suffer easily from blisters even during single day walks, and they now use the Ducktape method as a preventative measure. They apply the tape beforehand and say thet it has worked for them, and have not had blisters since using it.
My thoughts are that it may be okay for single day walks, but on multi day walks, you would at least have to remove it overnight and re apply in the morning.
In the instruction on how to apply in the link, he says that you can remove and replace the same heel cup. I am not sure about that.
Something else to try!