7:43 p.m. on June 1, 2011 (EDT)
Hi nworbled,
When I buy boots I size them (or get fitted) while wearing a liner sock, as well as a expedition weight (thick) wool sock, and I make sure there is room to spare. This is really the only way I know to make sure I get boots big enough.
Not having enough length or width in your boots can really be hard on your feet, especially in steep or rough terrain.
Carrying a pack for 4 days is enough time to tell if your set up (socks & boots) is working or not, and I'm guessing you probably knew by the end of day one.
Carrying a pack day after day is way different that going for a day hike, as you know, but it's one way to work out the kinks in your set up. We all learn as we go, sometimes it's through asking or reading, sometimes it's through experience. (I've learned a lot the hard way)
I almost always wear liner socks, my feet simply do much better over the course of a multi day trip if I do. I also carry three pairs of wool socks and change often keeping my feet dry. This is very important, damp feet do not resist abrasion well because the skin softens.
Liner socks add more cushion, wick water away from your feet, and help to reduce friction. They also take up more room in the boot, as you say.
Beyond wearing good socks, changing frequently, and addressing foot problems before they turn into blisters, you must have boots / shoes that fit your feet properly.
I have bought more than one pair of boots in the past that just didn't fit well and ended up getting rid of them.
If you are in doubt that your boots fit correctly I would go try some more on and take your socks (liner & wool etc) with you. It wouldn't hurt to take along your current boots for comparison. If at all possible go to a store who has someone trained to measure your feet and help you find boots that fit the shape of your feet.
Getting a boot that fits isn't always easy, be willing to try different brands. Different brands can have slightly different shapes, or may offer wider or narrower sizes to accommodate your feet.
Boots aren't cheap, but your feet are priceless when you are in the woods 20 miles from your vehicle.
I like Thorlo socks, as well as Smartwool & Wigwam, I would certainly try out some of their liner socks. A neat, flat toe seam is very important so make sure to look for that.
I'm glad you got to go packing, sorry about the foot trouble. I've been there, believe you me.