Life becomes rather simple and directed while walking the Camino de Santiago. At the most basic level, you walk, bike, or ride your horse from one village to the next, find a place to stay, shower, do laundry, and then have something to eat. Part of the daily routine (most days) is laundry.
Everywhere you stay will have laundry facilities. While occasionally you’ll come across a machine or a service for a few Euros, most days you do a quick hand wash of your clothes and hand them out on a line or drying rack.
So, you’ll need the basics: laundry soap and clothespins.
Many use bar laundry soap and a brush to clean their clothes. They travel easily and well and are effective at cleaning clothes. Personally, I chose to fill a GoToob with All laundry detergent. I love GoToob—they have locking lids. (I used them for my shampoo, too). One drop of liquid detergent was more than enough to wash out a pair of paints, underwear, a shirt, and socks: a quick swish, rinse till the water runs clear, a solid ringing, and then up on the line or rack.
It’s worth noting that most hiking clothes now include antimicrobial elements, so they don’t get smelly. While many pilgrims wash clothes everyday (it becomes the routine), you could certainly go a few days between washing. As with all things, this is a personal choice.
For clothes drying, I left behind the clothespins, choosing instead large, diaper-size safety pins. The upside, the safety pins kept the clothes on the line no matter the wind and they could be used for other things. The downside, clothespins keep the clothes in one place on the line while safety pins slide. Maybe a few of both would be a good choice.
Another consideration: you might want to pack a few feet clothes line (or retractable one). There were a few refugios that didn’t have enough space or that didn’t have any lines. Being able to string your own for a few hours could make a difference. The cord could also certainly serve multiple purposes. I didn’t have a retractable line the first time, but it would be a nice addition on my next Camino.