https://sims4studio.com/thread/9612/mini-tutorial-easy-weight-assigment

Hi ! I am TsminhSims

Today I want to share a small trick to save your time when assigning weight for hair.

This tutorial is going to show you how to assign two bones :

b__Head__

and

b__Spine2__

for your hair mesh smoothly.

Change into Weight Paint mode.

Step 1:

Create new vertex group and follow step to step in image below.

Please remember that the cyan line must be horizontal with the shoudlers

Step 2:

Clone that vertext group

Step 3:

Invert that vertext group.