In reply to davidandchrissie:
I can't comment on your whole itinerary but I have done one section you're planning to do
Similar to your day 4-5 from Collado Jermoso to Vega de Urriellu.
We set off from Fuente Dé and took the cable car up onto the plateau, the path then I think picks up close where you would join from Collado Jermoso and heads up and over to Vega de Urriellu.
In terms of distance I think this would be a perfect moderate stage for a multi day walk. We got to Vega de Urriellu for a late lunch and would have been a lovely place to stop. Instead we powered on down to Bulnes which was doable but too far to be enjoyable and turned into a bit of sufferfest, I had such bad DOMS the following day I could barely get going!
The paths for the most part are very easy to follow, think an unmissable superhighway of scree tramped down into a clear path with cairns and little daubs of paint. The daubs of paint have the route number written in them so like "781". However, you definitely would still need a map and compass just to make sure you're picking up the right junctions but once you know you're on the right path you could enjoy the hiking with just the odd glance at map. We went very end september and about lunchtime got caught by very poor visibility in the first snow flurry of the year and had to using pacing and micro-nav to find the Vega de Urriellu. It's definitely some of the most serious navigation ive done. That said in June you are unlikely to have any snow storm issues. But as always, if you expect the best and prepare of the worst you'll be well set.
There are hiking paths which are marked 'hard' some of these have a few very short scrambling sections but some are totally unremarkable and not all 'hard' paths are equal. On the way down to Bulnes we met 3 guys heading up to Vega de Urriellu, all in their 70's and one guy was blind. Absolutely still loving it. There was one section of the path down to Vega Urriellu (down the back of horcados rojos) which felt sketchy, but it's hard to make a comparison with summer as when we went it was covered in a couple cm of snow so felt very insecure, in summer might be a total jaunt. There were certainly no technical difficulties, maybe just about qualifying as very easy scrambling but it was very exposed and if you did some trip and stumble you could fall fatally. You'd want a head for heights but definitely no where to use a rope or technical equipment.
Got me reminiscing about one of my most treasured holiday memories, i think you'll have a blast!
(Definitely would recommend a set of walking poles)