I can't say I agree with that suggestion. Breloom takes a ton of experience to level up once it reaches around level 50 and you can't evolve it until level 53. Shroomish is terrible when it's IV bred and EV trained, so I can't imagine using one in-game for Spore. Your time is much more efficiently used training a superior in-game Fighting-type, and Blaziken is already perfect for that role.
I don't know what Absol is really doing for you, and you get it late and at a low level.
In terms of movesets, use Sky Uppercut/Blaze Kick for sure. I like the combo of Bulk up and Strength to set up on pokes that give you free turns (like Drake's Shelgon), but you can be more aggressive with Fire Blast and Hyper Beam in the last two slots since you can switch it out after kills.
Manectric wants Thunder, Thunderbolt, Thunder Wave, and uhhh who cares? Bite is good to beat weak Ground-types. RNGing for Hidden Power is a major waste of time in-game.
Milotic should be running Surf and Ice Beam. The rest doesn't matter, but Recover is definitely a great choice, and either Rain Dance or Hydro Pump can provide some extra power.
Swellow can run Return, a Flying move (Fly is the strongest but prolongs battles), Facade to take advantage of guts, and a filler, maybe a second Flying move or (lol) Steel Wing,
Gardevoir should be running Thunderbolt, Psychic, Calm Mind, and Hypnosis.
The last Pokemon to replace Absol should be...nothing? Honestly, you're plenty well-equipped to beat the Elite Four. Kyogre is plenty fine when you capture it, and Drizzle can help Milotic and Manectric. I can give Battle Tower advice but that takes real strategy and seems to be far on the horizon.