Realized the easiest way to do this is in a Triple Battle. First places that came to mind were Restaurant Le Yeah, Le Wow, and Sushi High Roller in Lumiose City in XY.
Enter the Triple Battle with a Pokemon with Damp, (Golduck, Poliwrath, Quagsire, etc,) a Pokemon with SD/Explosion, and Smeargle. Make sure your exploding Pokemon is only slightly faster than your Smeargle, so Smeargle moves directly after your exploding Pokemon. For this reason, the best Pokemon to use are Stunky, Drifloon, or if your Smeargle is high level, Volcanion.
If everything is correct, you should be able to go into a Triple Battle at a restaurant, select Explosion and Sketch, and come out of the battle with an Exploding Smeargle.