If you fly to Coruna:
There aren’t any buses from Coruña airport to Ferrol, you must take a bus
from the airport to Coruña city
http://www.autoscalpita.es/HorariosASC.htm#
A Coruña - Airport line Service run by ASICASA which joins A Coruña
(Puerta Real) with the airport, with stops at Casino, Plaza de Orense,
Avenida A. Molina, Alcampo, Portazgo, Corveira and Vilaboa. Journey
duration: 25 minutes.
Timetable: On working days, both from A Coruña and from the airport,
buses run from 7.15 am to 9.45 pm every half hour. On Saturdays they
leave from A Coruña every hour from 7.30 am to 10.30 pm, and from the
airport from 8.00 am to 10.00 pm also every hour. On Sundays and
bank-holidays they leave every hour, from A Coruña from 8.30 am to 10.30
pm, and from the airport from 9.00 am to 10.00 pm.
Price: €1.25. Information telephone: 981 231 234
Then you must take a bus from Coruña to Ferrol. (
http://www.arriva.es)
If you fly to Santiago check
http://www.monbus.es/index2.htm
Click on "Horarios" to find timetable.