Hi Laurie! Since you've done the Primitivo already a couple of times, I can understand that the idea of doing the Friol-Sobrado detour appeals to you; however, we (my two hospitalero mates and myself) are delighted to hear how much you would like to come here again
We'd be sorry if you didn't
Sorry, can't tell you much about that route from Ponte Ferreira to Sobrado; I guess you could use your smartphone (if you have an internet plan in Spain) to use googlemaps to follow the route; part of it follows roads and would be easy, but the part off-road is not so likely to be easy at all!: you might find some fenced paths, fields used by cows who won't let you walk near them, crops that you can not walk through, etc... Maybe... a bit risky?
Another chance is to walk back from Ponte Ferreira about a mile and then take the road LU-231 North to Friol:
View attachment 24184
It is a less adventurous option (more road walking), but gives you the chance to visit the Friol castle (Fortaleza de San Paio de Narla), which is certainly interesting!
Feel free to ask any questions you want! Glad to help if I can!