Frightened ‘true’ ferals will try to find a way to escape. They will go to great lengths, climb walls, jump great heights, break through dropped ceilings, squeeze into holes, scratch/gnaw through things to the point of bloodying and hurting themselves. Confinement and human interaction is generally not in their genes – although some ferals respond remarkably well to a life with humans. It really depends on the cat. Some are born in the wild of course, and stay wild and others are abandoned or lost ‘pets’ that might remember their former human interactions, good or bad.
But in order to be successful in your endeavor, put them in a SOLID room in your barn that has no potential escape routes – your tack room hopefully – not a makeshift, gerry rigged stall, unless YOU go to great lengths to make it secure.
If you decide on your tack room, I would take any tack or stuff you use daily, out of the room (so as not to frighten the cats by your constant comings and goings) – I would also provide a snuggly set of ‘hiding boxes’ where the cats can retreat and feel safe when you do enter. They need to know they have a safe space that is their own. However, some ferals who are bent on getting out, will make a run for it and dart past you and out the door the second you open it. So be aware that this is a possibility.
I would definitely plan on keeping them in the room until they are eating their food in front of you – and/or are showing clear signs of not being deathy afraid of you. The length of time depends on how ‘desensitized’ the cats are to humans when you got them. The shelter should be able to give you some indication of how ‘wild’ or human hating or human tollerant the cats actually are.
Acclimatizing feral cats can take weeks. So be prepared to go the distance. And it’s often best to not force a cat to interact with you. Best to just feed – go about your business and leave the cats alone physically.
But…voice is another matter! You should decide on a phrase you will use whenever you’re with the cats – Hi kitty kitties – or something else. You should repeat the phrase often, especially at feed time. The cats will learn this sound and remember it as a good thing. And beleive it or not, cats respond to being named – and having their name called.
The most important factor of all is feeding ‘time’. Plan to feed the cats at the exact same times every day. Cats are very in tune with ‘schedules’…they know, just like horses, when it is feed time … and should your cats escape or disappear at some point, they will probably return (or lurk out of sight) at their scheduled feed time. So once the cats are ‘out’ either through escape or by you letting them out, continue to feed at those times in a designated area – the same place every time even if you don’t see the cats.
If you are a real cat lover – no judgement if you aren’t 
– you could keep the cats in a room in your house until they are desensitized and know where ‘home’ is and know where food is. Then you could gradually et them explore the outside world - the barn, etc. Since feral cats often prefer to be outside, they will soon want to live in the barn where there is lots of stimulation and things to do – and food too that you will continue to provide.
Worst case scenario: cats escape before they know where home is – your barn or your house-- and are never seen again. It could happen. You’'ll of course feel bad. But…cats are very resilient. They know how to survive. And if you had a reasonable amount of time with them – a long enough time where they’ve learned the sound of your voice, know their names and know food is available…they just might return if you make an effort to ‘call’ them. And you should also leave food in a designated area at the same times you were previously feeding. Just because you don’t see cats, it doesn’t mean they aren’t still around.
Best of luck! Hope it works out!
