I spoke with someone who makes prosthetic legs for amputees. She told me that they recommend a womens nylon under a sock to help prevent rubbing when a patient is first using their new prosthetic leg. When she heard about our trip she told me to buy some knee high nylons to wear under our normal socks to help prevent blisters. She says it works like a charm for amputees. Anyone ever heard of this or tried it?
Back when I had heavy old leather hiking boots, I always wore a CoolMax "liner" sock under my wool socks. Same theory, but the liner sock is more durable than a knee-high nylon stocking. You can still buy them at outdoor supply places.
For our trip to Paris (2 weeks, 6 days away, not that I'm counting down!) I bought Wright socks. They're double-layer socks with the same idea. The inside sock rubs the outside sock, so your foot doesn't. I've used them for years. They work great to prevent blisters.
Wearing properly fitted shoes and socks should prevent blisters, but yes, this trick works quite well if your footwear is not "broken-in".
I have a few pairs of the double lined socks, and while they take a while to get used to, they work really well for preventing blisters. Also make sure to get socks that are not cotton (synthetic helps prevent blisters as well and they won't smell as bad).
Blister sticks are available as well for trouble areas. Basically it is like a deoderant stick that you put on and it helps lubricate the chaffing areas. You can buy them at sport stores.
I tried knee-high nylons under lightweight socks for a trip to New York City when I knew we would be doing a lot of walking - and I had an incipient blister [a red, tender spot on my foot] from incautious choice of footwear the day before the trip. It worked fine and was cooler than my double-layer WrightSocks. A couple of pairs of knee-highs take very little room.