What's a great product/hack for removing stubborn poop stains from baby's clothes?

First thing's first, when you spot a poop stain immediately rinse it off under some cold water. If its not too stubborn, it should come off in just a single wash. If it's too stubborn, you'll need to pre soak the article overnight with enzyme-based stain remover. Wash with a quality detergent in hot water and before drying, check the stain again. Repeat this process if you need to.