Best Route to Barajas International?
 

I will be traveling in Spain soon and I am trying to figure out the best route from my hostel to the metro ending up in Barajas International Airport. My hostel is closest to Bilboa station and Alonso Martinez station. What is the best route to get to the airport from these stations. Also, are there usually bus stops that can take passengers to the metros?

Need to clarify...I will staying in Madrid near those stations. Forgot to mention that.

From Bilboa, take Line 4 destination Parque de Santa Maria and change at Mar de Cristal for Line 8 to Aeropuerto.
From Alonso Martínez, take Line 10 destination Hospital Infanta Sofía and change at Nuevos Ministerios for Line 8 to the airport.
Remember there are two metro stations at the airport: for terminal 1-3, get off at Aeropuerto T1,T2,T3; for terminal 4, two stops further at Aeropuerto T4, where the line terminates.

Line 4 now terminates at Pinar de Chamartin .

Thanks.