French milling (aka milling) is a process that the average small-scale soap maker cannot do. You need specialized rolling equipment to mill soap. Cool, dry soap is pressed between chilled metal or stone rollers to make the soap harder and more dense. It's sometimes called "French milling" because the process was first developed in France back in the day.
The term "milling" is sometimes incorrectly used when people really mean the process of "rebatching". Rebatching is the process of heating soap usually with a bit of added liquid until it forms a thick paste, and then pouring the paste into mold(s). So heat and liquid are required.
Not sure which method you're talking about, so I'm explaining both.
I have no advice about the paper nor the recipe you're looking at.