Apparently your already found it, because you just posted in it.
VOLT is too difficult for me. I have always used the method described in the Tutorial thread — Adding OpenType Features. Understanding how to write the script with the correct syntax is initially somewhat difficult, but with an example to follow its just a careful copy/paste job to modify the script for one’s own use. It took me less than a week to get up and running with it.
Still, if you want, keep the thread going telling us about your progress with VOLT. The discussion may be helpful to others.