I let mine mingle for a few days during the day with their own house for the night and then just move the one batch into the other house at dusk and close off old house. When I did this last time I actually had to isolate the cockerel for a few nights as he wouldn't tolerate the new girls in his house. It all sorted itself after less than a week. You can also mix them up overnight, by moving a few from one house to the other and vice versa, so its a complete re-arrangement, then re-arrange again in the final house by putting them all in there for the night.