Mostly on solo hikes and peak bagging climbs, not on real approaches. If I'm with a partner we usually have a schedule and need to hoof it - shod. Have done it with fairly heavy packs but I need to train up to that. Boots do add a lot of stablization that you have to make up wioth muscle and balance.
Start off on good trails close to the road (usually less debris in the first mile, eh?). Hike barefoot until you want to or need to shoe up. Might be a short distance at first, depends on what you step on haha. But if you make a habit of taking off your shoes for parts of hikes very quickly the bottoms of your feet will toughen up. Only takes 2 or 3 consecutive weekend hikes to start getting stronger feet.
If you rock climb you will notice nearly IMMEDIATE benefits, I shit you not.
On the pain front - I already mentioned the build-up piece. OK.
I rarely do a lot of cross country barefoot work. My feet aren't THAT tough and I'm not going barefoot as an end, its a means to an end. And I'm not into thistles and thorns and a zillion pine cones can cripple ya.
And yet I find long stretches of most any trail are good for some barefoot work. As I did more I found I enjoyed it more, for aesthetic reasons; quiet, omg its QUIET! If you ever hunted in your life, with firearm or camera... you will appreciate the utter silence you can achieve.
And also, I love seeing my barefoot prints in the mud for some stupid reason - its WAY CAVEMAN bro!
I find I can't do much heel walking barefoot. Try it and you'll very quickly come to understand how the foot works and why a dog's foot is so different from ours. Dogs sure don't walk on their heels, I can't think of any animal but humans that do and we can only do it with shoes on.
So I'm walking down the trail barefoot. At first I'm cautious, afraid I might cut my little tootsies and ruin the day. But soon I'm just walking, not really thinking about the trail anymore, just accomodating the changing conditions as they come, like you're supposed to.
When I just walk? Don't think about it? My foot knows where to land. My brain knows how to direct it automatically. Not surprisingly I found I knew how to walk barefoot, its wired into my very DNA. How could I NOT know how to walk barefoot?
Naturally I walk on the balls of my feet. The reason is pain. See when I come down on the balls of my feet, if I happen to step on something sharp it seems like my leg muscles automatically adjust. Its like automatic - I don't have to think about it. My brain won't let me put too much weight on the ball of my foot - it automatically buckles the leg and the other leg takes the weight.
AS I got more used to it I realized the bottom of my foot has all these (this sounds weird) micro-adjustments. By coming down on the ball, I can actually wrap my foot over some sharp or pokey object, get weight on that foot but not cutr or hurt it, all in real time, all without thinking about it. Just walking.
Pretty soon I'm walking on pine cones for long stretches and really sharp rocky sections don't scare me as much. I can only do so much of either mind you and sooner or later the cut will happen. But its enlightening to try it.
Now what I found? Particularly going down hill the temptation to step on the heel is still there. Yet if I do? Well, there are NO microadjustments in the heel, that's the thing. I seem to get ONE SHOT to land it. It lands where it lands and the entire weight of the body comes down on it and there ain't shit I can do about it if there is something sharp there. Further, there are far fewer nerve endings in the heel so I often can't even feel the object till its too late. The leg never gets the chance to buckle. Cut, in the blink of en eye. And cuts aren't the worst of it - a heel bruise is unbelievably cruel.
So that's a book I know but I have had really good results from it and come to enjoy it for its own pleasures. And it really changed my attitude about walking down hill. My bro Burl tried to get me to see the light about a decade ago... but no, I had to do it MY WAY.
ps. And to tie it up, my knees don't ache nearly as bad after descents where I resist the heel walking temptation.