As for the one that tapped them for eating an unsanitary substrate ... that's not something I'd ever condone.
Nor would I, just saying that's all I could find about "training" them! I wouldn't do such things to my many doggies, so I wouldn't do it to my beardie, either.
Just for fun, I started working with her(?) with the clicker and some crickets. At the very least, it seems that s/he's much more excited when I approach, doing a little dance and scratching at the front of the cage, and has already "gotten" that when I put my hand in front of her, she's supposed to hop on. I don't know if it's because she's learned anything, or because she just enjoys a bit of a snuggle.
I'll see, I s'pose!