If it's production, you can go to Shenzhen Jewelry Industrial Park, Panyu Jewelry Industrial Park and Shunde Lunjiao Chow Tai Fook Zhou Shengsheng to see if they are hiring people to be trainers.
If you want to learn, there is Zheng Jingzhi Vocational Middle School in Shunde with a jewelry major, and the most famous one in China is China Geo University (Wuhan) Jewelry College, which has jewelry testing, jewelry design and so on.