Hi, I walked the camino del norte from santander in june and july of this year.
The stretch you talk about is quite hard not just because of the distance but the topography and the terrain. After the camino splits off( to the primitivo) within a few kilometres you have quite a long and steep climb(But the views to Gijon just after the peak are worth it) you then descend into a valley which is quite easy to get lost in. Then if you are on the correct path you start to ascend again this is a bit shorter than the first ascent but a bit harder in that the path goes up quite rough terrain then after that it can get quite confusing because of land slips. I dont mean to put you off, but it was a hard day(and i started from villavicioasa). However you do have pilgrim accommodation before Gijon on the campsite 'Camping Deva' there is a website for it. I didnt know about this, but i met people who stayed there and said it was quite nice because you had access to the swimming pool.
If i ever do the camino del norte again(which hopefully i will in its entirety) i will go to oviedo by the primitivo then cut up to aviles(which quite a few people do), the reason for this is that the camino between gijon and aviles is one of the most awful stretches of walking, alot of it is urban, you walk past industrial plants in gijon(about 5km from the centre where i started), and then after about 8km of country walking, your back along side a busy, dusty, dirty, dual carriage way which themselves are along side smoky industrial plants and its like this all the way to the hostal in Aviles.
Hopefully someone else may have additional information to this, and there may have been another set of yellow arrows which i completely missed and bypassed this awful days walking.
Im not sure if this is going to be of use for you, but it was nice remembering the walk.
Buen camino