Sorry, have been off-line unexpectedly for the week-end.
www.alsa.es have a bus departure from from Santiago da Compostela at 10:00 (Spanish Time) routing via Porto and arriving Lisbon Oriente at 18:00.
There are no direct trains between S. de Compostela and Porto.
You would need to get the 05:50 from S. de Compostela arriving Vigo at
07:37. Then the 07:40 from Vigo arriving Porto at 09:55 (Portuguese Time) Then the 10:52 from Porto arriving Lisbon Sta. Apolonia 14:00.
See www.cp.pt for more info.
As regards booking tickets, Bus Station in Santiago is probably the best.
For trains, probably Vigo Station for the Sector Vigo to Porto and then Porto station for the Porto to Lisbon.
You can try the only websites from bookins but they can be difficult and slow at times.
You best bet is probably the bus as you should be able to book a through ticket.
