Smeargle is a Pokémon you can catch fairly early on (Route 2) and is an excellent breeding assist in the Egg Group it’s found in. The best, really.
Field Egg Group is the largest Egg Group, with Pokémon as varied as Skitty and Wailord both belonging there. Any Pokémon in the Field Egg Group can thus benefit greatly from Smeargle when it comes to transferring Egg Moves, and Smeargle often plays a big role in starting a chain breeding session that jumps across Egg Group boundaries.
The reason is because Smeargle can learn Sketch, its signature move. Sketch only has 1 PP but using it after the target Pokémon uses a move makes Smeargle learn that move. Yes, Smeargle can learn any move! (Well, except Darkrai’s Dark Void.)
This means any Pokémon in the Field Egg Group can learn any combination of Egg Moves without needing to chain breed. Simply have Smeargle Sketch the move, then relearn Sketch at the Move Tutor in Mount Lanakila’s Pokémon Center, and Sketch the next move, until you are done.
How to Have Smeargle Sketch
Unfortunately, in these games there is currently no way to purposefully trigger a Double Battle so that you can have Smeargle Sketch your own other ally. Instead, you’re going to have to use a bunch of wild Smeargle. It’s a bit roundabout but don’t worry, it’s not as complicated as it looks!
First, you will obviously need a male Smeargle, so go to Route 2 and catch one. After catching Smeargle, teach it Sketch again either by training (Smeargle learns Sketch at each multiple of 11) or using the Move Tutor in Mount Lanakila’s Pokémon Center.
Next, make your way back to Route 2 and find another wild Smeargle. Make sure to lead with the Pokémon whose move you want to sketch, with your Smeargle waiting at the back.
If you want to Sketch a status move (that doesn’t involve Sleep) or a very weak offensive move that will not kill Smeargle, immediately use it on the wild Smeargle. After the wild Smeargle Sketches the move, switch in your own Smeargle and Sketch the move from the wild Smeargle.
However if you want to Sketch a stronger offensive move, first use False Swipe on the wild Smeargle to lower its health and to make it Sketch False Swipe. Next, switch in your Pokemon with the move that you want to Sketch. After that, use an Adrenaline Orb and patiently wait for the wild Smeargle to call for another wild Smeargle.
If another Smeargle doesn’t appear, just spam the Adrenaline Orb–this won’t do anything, but it also won’t consume an additional orb, allowing you to waste a turn. Once there are two Smeargles on the field, KO the weakened Smeargle with the move you intend to Sketch. The freshly-summoned Smeargle that’s still around will Sketch your move.
Now switch in your own Smeargle and Sketch this move. At this stage, it’s important that your own Smeargle is strong enough to survive the other Smeargle’s moves! So take it through the Elite Four or do some Chansey chaining. Afterwards, you can repeat the process until you’ve filled your Smeargle out with all the Egg Moves you want.
In the event that a wild Smeargle appears after you use False Swipe, but before you switch your Pokemon, you will need to KO the Smeargle that just appeared. Also, if you’re not planning to stack multiple moves on your Smeargle, or if this is the first move you want to Sketch, you can just capture the wild Smeargle after it’s Sketched your move.
Note that moves that hit the whole area are near-impossible to Sketch, but the big ticket moves like Surf and Earthquake are TMs. Another method that you can use if you do not want to do this setup is simply find a wild Pokémon in Alola that knows the move and have your Smeargle Sketch directly off of them.
It takes patience because you will have to wait for them to use that move, and for some moves it is impossible, but it is a good alternative method.
A Smeargle for Thoughts?
Because of Smeargle’s versatility, you can (and maybe should) make a Smeargle for S.O.S. Chaining too. Having a Smeargle know False Swipe, a move that can KO Pokémon but with lots of PP, and Spore or another status move can make it an all-purpose S.O.S. Chaining and catching too.
That way, you don’t have to constantly switch Pokémon. And if you need to trigger a weather-specific SOS, the fourth slot can be Rain Dance, Sunny Day, Sandstorm, or Hail. Make sure you equip Safety Goggles to Smeargle if triggering the last two weather conditions so you don’t take chip damage.
You’ll also want to make sure the Smeargle is at a very high level because its base stats are absolutely absymal. You might even want to EV train its Attack too.