Since you have asked, here are a few more thoughts:
1. When leaving Porto the first time, I simply walked through the city. Not a bad walk, but not everyone's idea of a good time. The second time I left Porto, I took the metro up to Matosinhos and started walking from there. If I ever do it again, I would start at the Cathedral, walk down to the river, and then follow the river to the ocean. Once at the ocean, turn north and continue up to Matosinhos. It would be something like 12-13 kms, so it would make for a good warm up on the first day. I have covered parts of this on the tram and on foot, and I think it would make a really pleasant walk on a nice day. Once in Matosinhos, you can find accommodation there, or take the metro back to central Porto, and then back out again the next morning to continue up the coast.
2. When arriving at the ferry dock at Caminha to cross the river to Spain, we were told that there was a 5 hour wait because of the low tides. So as we were sitting there wondering how to kill the next 5 hours, someone driving by stopped and suggested that we walk up to the beach near the mouth of the river (about 3 kms) and ask for Mario. If we could find Mario, he would take us across. We did that, easily found Mario by asking at a nearby restaurant, and he took us across to Spain in his little fishing boat for 5 euros each.
3. In walking from Baiona to Vigo, we followed the yellow arrows. It was long and tiring - not a bad walk, but a bit of a grind. One of the other Forum members
@Albertinho has posted this in a different thread:
"Another nice one is leaving Baiona. Once arriving at the bridge of Nigrán/ Ramalosa you can turn left and will find green arrows instead of yellow. The green ones lead you direction Vigo alongside the waterline and has beautifull views. The yellow ones lead you onto the albergue ,about 400 meters further on and into the hills to Vigo. I followed the green waymarkers and enjoyed it. The green waymarked path was pointed out by the hospitalero of the albergue by the way."
I have not tried this myself, but I certainly would if I ever do it again. I looked at this route on Google Maps, and it looks like it would be much nicer.
I hope this helps.