The above solution is great, however I firmly believe I have a faster method. Similar to the solution above, you will want to load up "Zarp's Fortress. Following this, go up and to the right to find your partner. When you go next to them, you will be thrown into a cage and there will spawn numerous crates and barrels around you.
You want to draw Storm Clouds above where you see the boxes. If you draw one too close to the cage, it will electrify you and you will respawn at the beginning. So, spam circles above with the storm cloud pencil, and aim to destroy all of the boxes in the area and electrocute yourself.
With this method, it only took me ten minutes to have this done. This was on top of the only natural progression that came from Pirate's Plunder.
Hope this helped!