I converted the deep to mediums a couple of years ago. I had 1 deep and 2 mediums as my hive setup. I found the queen in the upper medium and so I placed a queen excluder between the 2 bottom supers and waited for the brood to be born down below. Then I removed the deep super. The frames from the deep that had pollen, I cut down to the size of a medium frame and placed them back into the medium super. At this time, I only had one hive and that was easy.