Grease, and then if you don't want to use an entire patty case, cut circles out of baking parchment and stick in the bottom and then once cooled you can run a plastic knife delicately around the outside not to scratch the tin and they'll come out of the bottom perfectly. Always make sure you leave things to cool in the tin. Hot breads/muffins/cakes are more delicate than when cooled as they form a crust and come away easily.