I really don't think there is a definate cure! TJ and Roxy are 2 yrs. and I still have problems with this. It has gotten better but they still can't be trusted. I think TJ does it because he is in this constant (made-up in his mind) competition with Roxy. He doesn't want her to have ANY THING!
Roxy doesn't do it as much, but she can and will too!
I have just been trying to get it first. I have narrowed down there poop times. They will go 2x a day for the most part. I look for their 'have to poop' signs and then watch like a hawk. I praise and praise for going poop, then I pick it up and flush it. They know that after the flush then they get a treat - chicken jerky - their favorite!
My next and last resort will be the coins in the can. They are deathly afraid of the coins in the can. So, if this behavior continues into the new year, I will have to 'set them up' separatly - giving them the opportunity to eat it and then - SHAKE, SHAKE, SHAKE the can!