Walked it in May this year (2017). Had some very rainy days!
I purchased bus ticket the night before. Just to have it. Bus was about half full.
I rode the bus. Had three stops: Fatima (been there before, so was nice seeing it again from the bus), Leiria, and Coimbra (been there many times before).
Journey time is 4.5 hours. A single ticket from Lisbon to Porto costs €19/€9/€15 (adult/child/senior) and can be purchased online at
www.rede-expressos.pt or at the Sete Rios Bus Station.
Bus departs Sete Rios Bus Station in Lisboa and arrives at Casa da Musica in O Porto.
If you ride bus to O Porto, you can catch metro at Casa da Musica to center of Porto.
About the walk: I rode the local train a few stops out of O Porto. To avoid the traffic, factories, etc. I did not do the coastal route.
First stop was Casa Julia. She is wonderful! Good place to stay. Cafe around the corner from Casa Julia to eat at. When entering town watch for the signs for Casa Julia. It is one block off the main street in town.
Walking tours Lisboa and O Porto are great. If you have time I recommend them.
Good luck..