Sleep in your sleeping bag; bed bugs go first for exposed skin, so if there is none, they may head elsewhere. I don't take spray with me. With my sleeping bag and pack pre-treated, I have never seen the benefit of taking the spray. I don't think it is fair to hospitaleros to add chemicals to their property. If you see bed bugs, tell the owner, and go elsewhere (if you are bothered by it). If a place has bed bugs, you need to spray them directly. The most you will hit are the ones you see, so unless you plan to stay up all night spraying, you cannot kill them all. You may kill a dozen, but another hundred are waiting for you to go to sleep! Rely on the treatment to be the best protection you can get. I cannot imagine that you would like to be breathing the air as your neighbor sprays for bed bugs. Wet permethrin is the most danger to humans, so it is hard to treat space and let it dry in an albergue. If multiple pilgrims sprayed each day for the summer season, an albergue would become so toxic that it would be dangerous. The Red Cross building in Washington, DC had to close its basement. Someone tested it after years of rat poison treatments, and the accumulation of poison made the entire floor unsafe for humans. The Red Cross was saving flood victims, but poisoning its employees!
When you get home, put your pack into a large plastic bag, add permethrin spray, and let it sit for a day. Permethrin is a better insecticide than repellent, so it will do a good job of killing any live hitchhikers. Wash clothes and washable equipment in very hot water to kill any eggs you may have brought home. Spray your pack inside and out with permethrin, and put it in an isolated area inside the plastic bag. Bed bugs need food, so keep them away from a food supply (you and your pets).