This is what the current world record holder did. First, you have to play OR and not AS.
Choose Mudkip. Spam water gun against rock Pokemon and echoed voice against everything else until you get the TM78 bulldoze. Then spam bulldoze against everything.
When you get Latios, put it in your first slot and spam luster purge against everything, unless surf or dragon breath would be stronger.
When you get Groudon, put it in your first slot and spam earthquake or lava plume against everything. Give Groudon the red orb when you get to the Elite 4. After defeating Glacia, take off the red orb and swords dance sweep Drake and Steven.
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