Here we hide the body leaving only the head, a little of the neck and the hair.
Create a Material with 3 Sub-Materials as shown.
Let us start with the hair as ID 3.
A cylindrical mapping with the seam in the front. On the right-hand side the UV mesh. Note that at the top of the UV it is completely stretched out and not easy to adjust.
Start to adjust the mesh by moving it from the remainder of UV with the Expand Selection function from the base point.
Select the faces of the Scalp and apply a Planer Map.
Move the new set of UVs and scale them up to a Large size. We will be knitting the Scalp to the rest of the hair later.
Now adjust the remainder of the hair.
Separate the Scalp UV into 2 parts, use the dividing line from the center of the hair.
Select the identical points between the 2 sets and then Target Weld the points (in the top right). Adjust the remainder of the points correctly.
We do the same again with the other pieces.
The UVs for the Hair are finished and on the right is the object with smoothing.