Are there any border procedures to follow in driving from Portugal to Spain (Porto to Santiago de Compostela) and then back to Braga in Portugal? If so, are there places that are easier for border crossing?

We crossed the Portugal/Spain border several times and didn't even know when we crossed into the other country on some on the roads. There was less signage than entering a new state in the US.

As both countries are in Schengen, no border formalities - you just drive through. All you notice you've crossed is a change in signage (different language) and perhaps the state of the road. Also remember there's one-hour time difference, Portugal being one hour behind Spain.
Spot checks are possible, but not very likely.

I do not recall any border check on that crossing going from Portugal to Spain.

Hi; Last year we were stopped at the bordor by police. While it is not required, get a International Drivers Permit. Cost about $23 dollars with photo, at AAA. I handed him the IDP and my US drivers license and we were on our way. No Problem. On the way back into Portugal no encounters with police. Richard

Thank you all. Got all the info we need.