Not a simple user-friendly dialog, but the add-on explains it well enough that anybody who isn't totally computer illiterate will be able to perform this.
Just make sure that nobody is shoulder-surfing when running the script.

There are a couple things you need to do
- in console type allow pasting before pasting (ignore error about "Uncaught SyntaxError: unexpected token: identifier")
- use about:config and set general.config.sandbox_enabled to false
- The generated script has a wrong line on line 2 it should be typeof(Cc)
not typeof(Ci)
- afterwards toggle general.config.sandbox_enabled back