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I caught 6 Munchlax in a row. I found a Shiny in Platinum, used the Rare Candies I had been accumulating to calculate my IVs at level 50, which I then used to calculate my Secret ID. With that, I was able to use Filb's honey tree finder to find the four Munchlax trees in my game. I then slathered honey on those four trees several times a day for less than a week before finding a Munchlax. Then I just kept slathering the tree again after the battle, which causes them to chain.
Ended up with a bunch of Leftovers in a few days. But I continued to make use of my Secret ID by abusing the RNG to continue to find Shinies.