What is the best way to remove small, formula stains at the neckline of a young baby's onsies, dresses, etc.?

I've had three in diapers at one time so I know a little about stains. A gentle and great stain remover is called Bac-Out. It is an enzyme cleaner made by Bio Kleen. You can also fill a bucket or tub and soak the onsies with a denture tablet or two. Drying in the sun also helps.