All you need is:
An old scarf or some cloth shaped roughly like a scarf
A paper clip (or 2)
And a metal file
For knit cloth you probably don't need to sharpen it at all.
The small hook is probably better this way there is more room to hook the big one at the end.
If you are using 2 paper clips you probably want to attach them toward the edges.
Note: If you already have some sort of hat like me just pull it over your new one if you want to be extra warm.