First off - I offload a bishopric. Make sure that when you give away a bishopric that you get the 25 piety church grant bonus. Not all characters give it (and I haven't bothered to figure out why some characters don't). If you are keeping the county for yourself, then this is a great opportunity at the duke/king/emperor level to poach great characters from your realm's court so you can stock your council - you can grant titles to anyone in your realm, and then they come into your court.
Very good to know, thanks! Enjoying the AAR, and learning too.