I am working at the boom festival to promote a volunteer company, however am struggling to find out how to get there from lisbon airport. I am aware there is a boom bus but these according to the site have to be purchased in connection with the festival tickets and as I got the tickets from someone who is unable to go rather than purchasing them directly I did not book bus. Also I need to return to airport on aug 23rd, before end of the festival so I can't get the return bus back on 26th. I need to arrange alternative transport. Does anyone please have any suggestions? Idanha a nova is the location of the festival.