I guess I'm lucky. When Sweetie was 6 mo old, we trained her to swim. She had the beginning of MBD in her back legs and swimming would help with not only exercise, but with the proper medicine and exercise, the MBD was stopped. she still doesn't stand well on her rear legs, but they are stronger now than they were. To this day Sweetie swims the length of our bathtub, Swims a bit more against the wall of the bathtub, then poops and she outta there, in a flash, get me out! Then it nap time.
Lonzo on the other hand, is just recently adopted (1 mo ago) and he was careful to get off what towell, board, and poops beside it. He doesn't poop every day, but he has poops in bathtub a couple of times, so I'm hopeful he'll get into that habit, too. It's easier to deal with and it's not in the tanks at all, so that's also a plus.
But for beardies who want to poop in thair tank, that step by step works well. Thanks for the instruction, the pics sure tell the tale! Thanks