I hope I don't repeat anything here but I have not read the whole thread. When I introduce a queen I leave her in the cage in the hive for 3 days and then release her onto a horizontal comb on top of the frames and watch the reaction of the workers. If they seem to accept her I just lower the comb back into the hive. If they try to ball her I stick her back in the cage for another day. Introducing the queen to a nuc first helps even more. I never rely on the fondant method now as it's too hit and miss for my liking and has caused the loss of some good queens.

When I can't find the old queen or can't face searching a killer colony I just insert a protected queen cell. They can't tear down the cell and when the virgin eventually emerges they seem to treat her like a supersedure queen and the old one gets the chop. Presumably they allow the virgin to sort her out. It works almost every time but I have not deliberately counted the success rate.

The same technique usually works with a colony with laying workers too and I have no doubt that it is infinitely better than the book method of dumping your bees on the ground. I can't imagine how that idea ever caught on.