I would second what @martysville says about the train from La Coruna to Ferrol. I turned up at the train station 30 minutes before the train went to be sure I had a seat. Only about 20 people on a 3 carriage train. Tickets are available on the day from the ticket machines in La Coruna station, and they have English language buttons you can press.
Train is more picturesque than the bus, and from Betanzos, it follows where you will walk for the first 2 or 3 days in reverse.
La Coruna is a wonderful city to spend the evening, and if you have time, especially, if you have flown in from distance, spend the first morning in La Coruna also and then travel to Ferrol that afternoon. Spend the afternoon / evening exploring Ferrol, stocking up with provisions, and then start the Ingles on the following day (the second day after you arrive in Spain). The Ingles guidebook stages, if that is what you are doing, are long, and you probably need a day to get over your travel / jetlag before you start.