As a "Cradle Catholic" who tries to remain observant, I noticed on my three Caminos that Spain suffers the same lack of priests as North America. Accordingly, not every church you encounter in every village is operational. Or even if it is operational, it may be on a rotational circuit, with a Sunday Mass offered there on every "n"th Sunday. So, do not count on being able to find a Catholic Mass in every village you come to, every day.
Also, on a Sunday, you may end up in a place without a working church, or without a Mass scheduled that day. Relax. As one of the priests at Sanitago explained to me after my first Camino, just being on Camino exempts you from regular weekly Mass attendance if it is not possible do to geography.
The "BOSS" understands your motivation and intent (I demure from inserting another name here to avoid annoying the agnostic and atheist pilgrims in our merry forum, I DO respect your opinion.).
The entirety of your pilgrimage effort is considered a prayer, per se. You can confess missing the several Sunday masses you may miss along a typical month's long pilgrimage. But, trust me, it will not increase your penance for having sinned. If you just walked 783 Km from St Jean Pied de Port on the
Camino Frances, you have already done your penance. In fact, that is what I am told by my confessors more often than not at the Cathedral at Santiago. NO matter how debauched I was getting there, simply walking all the way does wonders...It's all good. Go figure!
On the other hand, as you approach a large metropolitan area, Pamplona, Logrono, Burgos, Leon, Astorga, Ponferrada, Sarria, and Santiago, there are more options to manage the pace of your progression so you can end up in one of these larger towns or cities on a Saturday evening or Sunday. Also, you are more likely to be able to locate a Mass using the internet. This allows ample time to locate a vigil mass the Saturday evening before, or delaying your departure on a Sunday until after a Mass. Do not worry about how you look, smell, or how you are dressed. Pilgrims have been passing this way for more than 1,200 years, Trust me, they have seen it all.
Taking a taxi or bus to jump ahead several kilometers is even permitted. Think about it. A thousand years ago, if some local guy pulled up in his horse-drawn wagon and offered you a lift to Mass in the next town you would go, right? Also, you would not have felt compelled to walk backward to retrace the kilometers you skipped over so you could attend Mass.
I have a few ironclad rules I follow scrupulously when on Camino. One of them is NEVER cover the same ground twice. Do not walk backward, then walk again to return. So, if you walked 10 Km before you realized your passport, iPhone, whatever, is at the place you stayed last night, get to a cafe, call a cab and go fetch it. Return by cab to the same spot.
Got the idea? Always make forward progress, never retreat... Better yet, ask the cafe guy or woman to call for you and ask them to place the "lost" item in a taxi and "send it to you." This happens all the time. The locals are innately honest. Frequently, they will do it automatically, without being asked, or expecting repayment for the service.
I have even attended Mass with my rucksack strapped on as I was walking past a Church. It happened when I arrived in the center of the town of Merida at 11:00 on a Sunday in 2014, just as the bell rang to signal the start of Mass. The church was full to overflowing I mean spilling out to the sidewalk), and I could not get all the way in to receive communion, but it all counted to the good. I clearly attended Mass. Several people tried to help me get in more, but the place was so crowded it did not help. So, I gave them the universal gesture for "it does not matter" - I shrugged my shoulders. They smiled, I smiled, All was good.
Many of the postings above are anecdotal and represent pilgrims' favorite experiences pursuing a Catholic Mass along the Camino (usually the Frances). These observations are all valid and should be placed into geographical order, according the whatever map or guide you are using, so you at least have some specific ideas for the places you come to along the way. My observations are intended to impart tools and techniques you can use all along the way to manage your Mass attendance, as desired.
Beyond this, asking at the albergue, local tienda, hostal, or cafe is a good way to obtain the local "skinny" regarding when the next Mass might be offered. As a general statement, many towns along the Camino try to have a pilgrim Mass each night at 8 PM. These are usually very profound and special for pilgrims. YOU DO NOT HAVE TO BE CATHOLIC or even Christian TO ATTEND. Invite everyone you encounter. You will be surprised at some of the outcomes. The older the church, the more profound the outcomes...
As another helpful clue, typically, there will be a group of older local women reciting the Rosary, in Spanish (duh!), starting about 20-30 minutes before the scheduled Mass time. For those of you not familiar with this long-held Catholic traditional prayer to honor Mary, the mother of Jesus, use Google or Wikipedia. it takes about 20 minutes "mas o menas" from start to finish. So if you pop in about 7;30, or see well dressed older women heading into the church shortly after 7:30. that is usually a good sign that there will be a Mass at 8:00. Check the doors for posted notices. Better yet, if you brought your set of beads, join in. The ladies will be please as punch to have you pray along with them, even if in English.
If some of your pilgrim colleagues resist tagging along, simply tell them to consider the 1,000 year plus history, architecture, and the stories emanating from those walls. If that does not work, offer to spot the first round of vino tinto after the Mass!
To inquire about a Mass in town, ask:
(EN) Is there a Mass today? At what time? Where?
(ES) ¿Hay una misa hoy? ¿A qué hora? ¿Donde?
Whew! I hope this helps.