Catch a Vanillish at Mt. Lanakila, evolve it, and then go to the move reminder and teach it freeze-dry. Then, go to Route 2, encounter a male Smeargle, and use freeze-dry on it. If it survives, it should sketch the freeze-dry. Then, you can catch it and breed it with a Vulpix. If the Smeargles can't survive a freeze-dry, switch between the Vanilluxe and something else until the Smeargle calls for help. Pick one male Smeargle, and use freeze-dry on the other one. The male Smeargle should sketch that. Then, catch that one.
There were too many sources for me to want to list them. If you still have questions, ask me in a comment.