Okay, I will use Sedgewick, my male shiny Koffing, and Tap-Tap the Red Nose, my male Diglett.

Sedgewick, start things off by calling up a rainstorm with Rain Dance. Next, attack Lily with a couple of Thunders. However, if Sunny Day is used, use Flamethrower instead.

Rain Dance ~ Thunder/Flamethrower x2 (Lily)

Tap-Tap, let's keep the tempo up. Start things off with Earthquake! Next, see if you can blind them a little with Mud Slap. Finally, fire off a Sludge Bomb at Blast.

Earthquake ~ Mud Slap (both) ~ Sludge Bomb (Blast)