Ah, you learn the parent wipe.
Hold both her hands and feet in one hand, and wipe with the other. It takes practice, but it keeps them away from the poop, and then you have clear reign over your poopy diaper killing spree. Once she's clean, then you can let her wiggle free and put on the new diaper. Just make sure you have like 3 or 4 wipes ready, and you're good to go.
By about one and a half to two, she will learn not to put her hands there when you changing her, if she's still in the crap pants then.
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Every time you think you've made it idiot proof, someone comes along and invents a better idiot.
?the end of our exploring, will be to arrive where we started, and know the place for the first time. - T.S. Eliot