The before-and-after pair
The post that proves the skill without a word of selling. Shoot the before the moment the dog hits the table, before the first pass of the clippers, while the matting and the grown-out coat are still honest. Shoot the after from the same wall and the same angle once the dryer is off and the dog is standing. The pair is the caption, and it does the selling on its own.
Example caption
Ollie at drop-off, and Ollie at pickup. Same wall, same angle, ninety minutes of work in between.