Extending Copy/Sync tasks for plugin


I’ve being adventuring in the land of plugins and to take it forward and proper encapsulate the created tasks I want to create classes that extends the Copy/Sync tasks.
I found little help on that on the documentation and/or on the internet.
Not being a java guru myself I find a bit difficult to understand what to do with the documentation.

As a test I’ve tried to enhance the class from the tutorial simply by changing DefaultTask by Sync. The @TaskAction notation don’t work anymore, so I tried overloading the doLast method, without any luck:

class GreetingTask extends Sync {
    String greeting = 'hello from GreetingTask'
    public Task doLast(final Action<? super Task> action) {
        action << {println greeting}
        return action

Obviously I’m doing something really wrong, and the next step would be overriding configure, but I fear I’ll find the same challenge.
So is there a project that does more or less the same thing and I could learn from? Or a reading material that focus on how overload the default tasks methods with new code.