I've been able to get one of my old dogs to baroo by making noises into a long vacuum cleaner hose. They get that look on their face looking at the end of it, and not knowing what it is. Then sometimes they'll be perplexed enough at it to give it a baroo.
Well how mean are you? Buy them a nice pig ear, and let them smell it, and then don't give it to them for about an hour. Carry it around. If that doesn't irritate them into giving you a much deserved "ear full", I'm not sure what else would. Be careful though, they might just sneak off, and tear up your pillow.:D
Vegas