no particular skills are necessary. It's always happened automatically in all of my games once the last heathen has been converted: Villagers run over to the encampment and 'transform' it. Just takes them a few moments (not minutes), you will not see any scaffolding or % completed. I have attached an image below.

Other players have said they've had to drop a villager on the mud hut once the last heathen has been converted to get the process going. I've never had to do that. I am on a iMac running OS X 10.4.11