I hike in only merina wool socks. I will tell a story about my son and a 50 miler Scout hike. The hike leader INSISTED that my son wear two sets of socks. Within the first two days, my son had several large and painful blisters. (No, it is not fun to have to comfort your son who you find weeping in the morning because his blisters hurt so much and he knows we have five more days.) I pulled parent priority and told the poor kid to wear only one pair of socks. The problem went away and he has now never worn two sets of socks again. FWIW