Ok, personally then i would try a different way, if the loft is reasonably near you, go get the birds in a basket and liberate them at your loft a few times, when you get the birds let them settle in your loft for a few days, keep them hungry and then let them out. Before you let them out make sure the old loft is completely closed up and the birds can't get in. Once they return to there old loft and find nothing there they will follow there tracks back to you where they will find food and water etc.
The birds will prob always take a trip back to there old ground but will return to you.
In the early 90's i had to move in a hurry, moved the loft on Saturday, let the birds out on the monday and raced them taking a 3rd in the midweek on the wednesday.
Phil