One of the many positive things about technology is microfiber fabrics. They're light weight. They're absorbent. And, they dry quickly. As you're planning for your Camino de Santiago, try out some of these products (towels, shirts, even pillowcases).
My advice: Be sure to purchase the largest one you can find (at least a bath sheet size). The larger format doesn't add much weight to your pack and these towels (when dried in a drier) can shrink. No matter how "good" you are about it, your towel will probably end up in a washer and/or drier at some point along your pilgrimage.
It's also worth noting that some of these towels (like the microfiber pants and shirts) can come with anti-microbial treatments. My one recommendation here is that you try out these products for several days/weeks at home before you travel, just to make certain you aren't allergic to the fabrics.