Here are some sites, channels, and videos that I found really helpful in my doll customizing journey.

Dollightful: really comprehensive process videos that don't rely on using tools that might be inaccessible for the average person

How to Restring a BJD

Video Faceup Tutorial

Making Clay and Resin Eyes

Making Resin Eyes

Making a Custom Dress Form

Tips for Doll Photography

I am not affiliated with any of these creators. I just found their tutorials helpful and interesting!