The nearest airport to the festival is Athens (ATH). From here you can get a train to Corinth which leaves hourly and takes approx. 1 hour 30 minutes.
Once at Corinth, you can take a bus to Loutraki which takes approx. 15 minutes (departing hourly) and then a second bus from Loutraki to Cariocas where the festival is held.
The nearest ATM is in Loutraki so it is strongly advised to bring enough cash for the festival once you depart from here.
Yes - all the numbers can be found at the Cariocas helpdesk.