I understand your apprehension about bribery. I wasn't going to do it either but ended up doing so after dealing with Mason being a horror to TT (which I now know can be attributed to his Aspergers) and Angus having major regression after Caleb was born.
After a few days (3 or 4) of the little one going willingly and being rewarded the choc bits ran out and I conveniently "forgot" to buy more. By this time the habit has been established and the praise that I was also giving them became enough to keep them going. When Angus asked for his chockie I'd tell him next time we went to the shops and he'd get a little reward then