Shaye is 3, and she also does this - she is kind of a messy eater, carrying food away from the bowl and dropping pieces along the way to be picked up on her way back to the bowl, and she inevitably gets food around her mouth while digging into it. When she's done eating she "washes" both sides of her face with her paws but then comes and wipes it further on us, the furniture, or whatever suits her fancy, so it is likely he's using the couch as a napkin since he's older and it's less effort to do it that way. But, checking his teeth is a good precautionary move, and maybe helping to loosen stuff if he has missing teeth.