I think it's important to first consider why horses are 'barnsour' or 'buddysour'... or more appropriately barn- or buddy-sweet. Firstly they're prey animals that live in a herd. They're 'hardwired' to feel insecure when alone without a trusted, respected leader. They're also hardwired to be nervous about strange places, etc. Also very often, they don't enjoy their 'work' for humans, for many reasons. So I would be working on changing the motivation for the behaviour.
Working with the horse in a respectFUL but firm & clear manner to develop a strong relationship with them as a worthy leader is vital. Also while that will make it more likely for the horse to accept & enjoy working for you, ensuring first & foremost there isn't anything that causes the horse pain/discomfort, such as a badly fitting saddle, and being more positively, not just negatively reinforcing, which can include tactics such as saddle suggested - some feed on the trail at strategic points, going out to a Nice Place to graze, going to meet other horses... etc.
Starting out making the 'tasks' you require easy for the horse, not asking too much is important IMO & one reason why I would be inclined to start out doing short walks/rides.
Horses live in the present, don't have an understanding of 'consequences' for events of past or future, and so learn by *instant* association. That's one reason why I strongly disagree with the idea of allowing them to go home but then working them at the barn. The turning around on the trail without being told has been & gone & forgotten by then - you've already reinforced the horse for it's behaviour way back when. Also even if the horse could associate the punishment at home with the 'crime', considering the motivation - safety in numbers & in a known environment, that usually tends to outweigh the punishment - doesn't make the scary Going Out With A Human any less of a worry. Thirdly, you're only achieving anything with punishment if it's done in such a way that the horse can learn how to avoid or 'switch it off'. Therefore another reason punishment needs to happen at the time of the 'misdemeanor' & cease the instant the 'bad' behaviour stops. What's the horse doing at home to be punished for?? Doing as it's told? How does it learn how to stop it? Lastly but not at all least another reason why I disagree with 'working' a horse in punishment relates to the second common motivation for the behaviour - Work with humans is a Chore. I strive to make it Fun to do as I ask, so the horse can enjoy the ride or 'work' as much as I do.
As horses learn from instant association, I don't believe feeding a horse when they return is a positive reinforcement of 'barnsourness' any more than working them at home is effective punishment. It - and more relavantly, getting off, quitting Work when you're home is further reinforcement of how nice the barn may be tho!