Smeargle? I never got to no smeargle dungeon...and I'm on silver trench!
Firstly you must get the friend are Sky Blue Plains. If you haven't gotten that, then do this mission:
Client: Baltoy
Objective: Escort to Spearow.
Place: Tiny Woods B3F
Difficulty: D
Reward: Friend Area
Wonder Mail:
2 ? 0 N 1 3 + ? ? 3 6 R
M T ? R 8 4 2 0 M X ? W
Then, you should go the board infront of the Pelliper Post Office. There you should see a Smeargle mission. I don't remember the exact name and details, but it basically talk about Smeargle not wanting to grow up or something. Anyway, after that you get a free Smeargle in your team. It can also change the design in the flag. You have to tell him to do it, then you do a random mission or just clear a dungeon. Then the next day you flag's design will change. The flag will change randomly. Eventually your first flag will return if you want it.