It is thought to be a  a defining characteristic that distinguishes a dog slave from all other slaves, is just how mouth orientated he is.
The level of expression that comes from is one of the pleasures that he provides, from the quality of his whimpering and begging to the  dedications of his boot licking.

It is deep within his heart to please his Master, that is his number one goal, you only need to train him so that he has all that is needed to do the best within his ability to please you.

When the pup has finished licking his bowl clean you need to training him to lick the floor clean of the bits that he has spilt, its your choice if you wipe his face down - though toy might think of this when he then licks your neck and you got dog food down there.

It is also part of his training to be able to eat when in Bondage to ensure that he can develop the needed balance, unless you like seeing him fall face first into his food.

For all my dogs I require that they leave the dish clean, so you need to know how much they can eat. That they clean the floor of any spills, and then bring the dish to me  for cleaning, waiting till I am  ready. I do not assume that dog slaves do house work, only slave do that.