Just been looking at the website of Porto airport and I find there is a twice-daily bus service between it and Vigo, via Valenca/Tuy. This seems to be in addition to Alsa's daily service Vigo-Porto. Might be of use for accessing different parts of the Camino Portugues
http://www.ana-aeroportos.pt/ANAIngles/ ... +Porto.htm
http://www.ana-aeroportos.pt/ANAIngles/ ... +Porto.htm