in my opinion, using gel insoles and such are avoiding the issue and are band aids. As far as nylons go and such, i do know of many workers on the Alaskan pipeline that used them to keep warm. As far as preventing blisters, who knows.
If youre not in the back 40 or at 40k feet to your destination, you can try some of those band aids at home, now. That way you can determine how they work for you. I sold alot of shoes in my lifetime and everyones foot is different. what can work for you may not work for someone else and that can go the other way too.
The gel insoles can be a bandaid, but dont count on them being a permanent fix. again, its something you will need to try. Preferably at home, before you go on your trip.
this is how i see it, most people are issued a pair of feet. even though you can get replacements, i think the OEM are better.
Also what you may want to look into is wool sox. I have bought for my travels marino wool sox and have used them ever since, just for my travels. I find that they dont feel wet even when they do get wet and they dont smell bad if i have to wear them more than one (1) day. By the way, i have done testing them at home and wore them one (1) week without washings day in, day out. They werent as fluffy as washed, but they held up. you can hand wash them and squeeze as much water out and then roll them up in a towel to squeeze out more water. They will dry, within reason (humidity wise) over night. At home i wear cotton sox but i have a boat load of them and a washer handy. not so on my travels.
If this is your first trip, know that there is alot of cobble stone in use in Europe. I dont know about other parts of the world, yet. But get something that is COMFORTABLE.
If you dont know, then head out to your local travel/sporting good store and start trying on some shoes/boots/ or whatever floats your boat. Remember COMFORT is job #1, #2 and #3. Style will be down the list and along with price. Remember that the streets/sidewalks of the world isnt carpeted, so test those shoes out on hard concrete/stone or whatever you can get your feet on. Stand in them for hours and determine how your feet like them. Once you find a pair(s) you like, then head out with the sox you plan on wearing and pound some pavement. Do it for at least 1 ~3 days and see how your feet likes them. If at all possible, wear them for at least a week daily and see again, how your feet do.
Also, if you can swing it, bring along a 2nd pair of COMFORTABLE shoes to swap every day.
one comment. Your feet will adjust to your weight. So if you loose/gain weight, expect your feet to adapt to your weight gain/loss. If that happens, dont blame the shoes.
Remember the saying...."if momma aint happy, no ones happy".? same goes for your feet.