My dog is mega picky eater too. I've been switching foods,& at the beginning he likes the change but gets bored super fast. In addition, I recently adopted a beautiful shihtzu who's owners feed only human food.
Because I know the benefits of eating dry food (dental-wise), this is what I do:
I make eating time a game
I take one Kimble at a time, and toss it rolling like a ball through he floor. My yorkie loves fetching balls, so he chances the Kimble and eats it. I tried this technique with our new furball, who had eaten human food all her life, and it alctually also works!
I think modeling helped too; the shihtzu saw the yorkie and it became motivational competence. Try it out & let me know if it worked
