Preditor door in front of your bob's. Five weeks should do but you can start sooner by getting them before the waddles turn white but they are flying around inside and have never been out. Once I tie up the bob's, I leave them alone to come and go as they please for a month or more. When they do that you get what you see in the photo, they come out and look around and get their bearings. These birds have been out quite a bit, Early on they would do as seen here and fly only to the roof. Not a problem, they are working things out.
I found that ferals seem to learn to trap easier and fly off sooner. If your training within 30 mi or so from the loft, ferals are a good way to go. Trap some and make prisoner's out of them till you have young flying around inside. Then open the bob's and let them do as they will, your gonna lose some of your traped birds but all the young one's will hang around. You get a half dozen breeding pairs in there and you'll have to shoot birds before long to keep from being over run. My ferals, all hatched here, have already hatched two nest's this year. My homer's I got last winter started with three pairs, turned into 28 birds the first breeding season. The origional six also settled here even though I got them about 20 mi from here. They were from the year before aqnd hadn't been flown.
When you start training to trap, just start letting bob's down one at a time. Drop a bob, a middle one, and do it that way for several days. Drop the middle one rather than an end one so they push just a bit getting in.
