Having just been to Santiago and almost unable to visit the Pórtico de la Gloria, I have some suggestions for pilgrims who wish to visit.
The safest way is to book online in advance. The guided tours are sold out weeks in advance, so that could be a problem for those who don’t know their arrival date into Santiago until a few days ahead of time.
A second way to get a ticket is to show up at the museum office in the early morning when they open and see if new tours have been scheduled. That happened several of the days when I was there; a few additional tours were scheduled throughout the day, in both English and Spanish. The office is to the left as you face the main (now closed) cathedral entrance in Obradoiro.
The third way is the cheapest but the least certain. The museum has given the Pilgrims Office 25 free tickets for unguided pilgrim visits, Monday through Saturday, always at 7 pm. (Note there are none on Sunday). It’s the Pilgrims’ Office that is in charge of handing out those tickets. The office has decided to offer them to the first people arriving at the pilgrims office to get their compostela. You MUST be in line to get your compostela to be eligible for these tickets; having gotten the compostela the day before will disqualify you. So if you’re not very very early in the line, you won’t get one of these. Problem is, many people who take the tickets don’t use them. The night I went up to the Pórtico at 7, only 12 of the 25 people even showed up. So you might be able to get in by just showing up at the Pórtico entrance, with your compostela, and seeing if someone will let you in if there are no-shows (the people at the desk told me there are usually many who don’t show). That is not, obviously, a sure way but it may work.
In any event, seeing the restored Pórtico is one of those jaw-dropping opportunities. I read that all of the paint that you see is paint that was uncovered from the cleaning, and it dates to a 17th (?) century re-painting, not the original Romanesque painting. No new paint was added; that seems to be a no-no in restoration.
Even though it may be somewhat of a hassle, perservere in your quest for a ticket. And remember our pal
@jerbear who waited 11 hours (yes that’s right 11 hours) in line to see it during the brief stint when it was open to the public for free. He described quite a chaotic and aggression-laden long snaking line, so we can be glad we have alternatives to that!