From Patras to Athen

Hello 

We want to travel from Greece to Italy this summer. And for this we’ll buy the 6 days pass. But to us it is not completly clear how we can travel from Patras to Athen. We know that there should be trains or busses and this tranfer is inclused in the pass. But how does this work? Where can we see where and when these buses and trains depart? Do we have to make any seat reservations? Is the pass (what has been filled out for the ferry) enough to board the train / bus or are additional forms needed? 

And for travelling back from Greece to Italy, does it work the same way?

And another question: would it be cheaper if we just bought the global pass and would buy the ferries to the islands and to greece seperately?

Thank you for your answers

Kind regards