While training new pokes I have been running some experiments in Elite 4 and found a nice variation to
@AsianKid 's typical speedrun that I think is pretty efficient.
In this method, only 4 pokes are needed:
Houndoom with Flamethrower, Dark Pulse, Taunt, Nasty Plot
Infernape with
max speed, Close Combat, Taunt, Swords Dance, Protect
Salamence with Moxie, Choice Scarf, Dragon Claw, Outrage
Gyarados with Moxie, Leftovers, Waterfall, Stone Edge, Taunt, Dragon Dance
The other 2 spots can be whatever you want. I've been using a Choice Specs Starmie with coverage and then a poke holding EXP share for training.
Lisa (Grass)
Houndoom holding Amulet Coin
-Flamethrower everything
Cameron (Psychic)
Houndoom holding Amulet Coin
-Taunt & Nasty Plot on Exeggutor, then Dark Pulse everything until...
-Flamethrower on Metagross
Joey (Normal)
Infernape holding Amulet Coin
-Protect, Close Combat on Ambipom
-Taunt & Swords Dance on Chansey, then Close Combat everything
Samuel (Dragon)
Infernape holding Amulet Coin
-Close Combat or Flamethrower once then Taunt/Swords Dance until Garchomp faints you
Salamence holding Choice Scarf
-Dragon Claw everything
Note: You're simply sacrificing Infernape here, but doing some damage to Garchomp first to ensure Salamence can sweep.
Alexa (Champion)
Houndoom holding Amulet Coin
-Taunt/Nasty Plot until Froslass faints you
Gyarados holding Leftovers
-Dragon Dance, Stone Edge on Froslass
-Waterfall on Arcanine
-Taunt & Dragon Dance on Blissey, then Waterfall everything
Note: Sacrifice Houndoom right away, do not faint Froslass with them. After bringing in Gyarados, make sure to not get setup by Destiny Bond; use additional Dragon Dance if needed. Make sure to have used at least 2 Dragon Dance's total before fainting Blissey; this ensures your Gyarados can Waterfall everything to victory and avoid getting Dragon Dance spam swept by Alexa's Gyarados. If things get weird and you have terrible luck (suffer multiple hits from Froslass due to Stone Edge missing, extremespeed from Arcanine, sucker punch from Zoroark, etc) that leads to your Gyarados fainting, you should be able to finish the battle off with Salamence/Starmie. With your Gyarados holding Leftovers though this rarely happens. If your health is low heading into Blissey, you can just continue using Dragon Dance if you want to continue healing via Leftovers. I do recommend having some Ice Heals just in case you get frozen by Froslass.
I spent many hours over the weekend running this method and it's money. I recommend giving it a shot, if you have the proper pokes & items.
Question: Why does Infernape need max speed? Can any other poke be used instead of him for this method?
Answer: Infernape needs max speed (31 IV/252 EV) to ensure it always goes first against Ambipom. It will get out-sped on occasion with anything less. With that said, any Infernape is viable, you just risk taking hits and potentially fainting. Other viable options are Blaziken with Speed Boost, Protect, Swords Dance, and Brick Break. A high ATK Salamence with Dragon Dance could probably work as well. Most other pokes will require using multiple Swords Dance/Dragon Dance though and at that point it gets pretty risky, especially if they can't learn Taunt. And things can really go downhill if Ambipom uses Low Sweep and lowers your speed. With that said, I certainly can't say I've tried every poke, it's very possible there are other good options out there.
Question: Both Houndoom and Infernape are holding Amulet Coins; is more than 1 needed for this method?
Answer: No, but it does make it less tedious so you don't have to continue switching 1 Amulet Coin between the two pokes.
Question: Why are you sacrificing Houndoom and Infernape in the Dragon & Champion battles?
Answer: Because they're holding Amulet Coin, ensuring you get double the payout. Plus, the initial damage done to Garchomp is key to the Dragon battle. Additionally, Gyarados holding Leftovers instead of Amulet Coin makes the Champion battle much easier.
Question: What happened to using Ambipom with U-Turn? Ninetales? Heracross? Electrode? Choice Scarf Gyarados?
Answer: Those methods and pokes are still great. But over time, as more players continue running more experiments, more efficient methods are discovered. This method is just better. It's smoother, more efficient, and requires less pokes.
Any additional questions/comments are welcome, of course. I will mention I do have an extra max speed Chimchar that I can sell if anyone is interested
Now, onto updating the OP...