Go into a battle against a Pokemon that knows Counter and send out a Pokemon that isn't Smeargle. Then, withdraw that Pokemon first thing and send out Smeargle. If the opponent used Counter, then use Sketch, and you'll get Counter. If not, then keep repearing until the opponent uses Counter on Smeargle. I forgot if Counter goes after Sketch or not, and if it goes before, then just keep Smeargle out, use Sketch, and hope that the opponent uses Counter. If it doesn't, then just reset and do the battle over again.