I will be staying in Kowloon. How do I travel to Jinlong Industrial Zone, Qinxi, Dong Guan

You can use the East Rail Line to reach Lo Wu where you can pass the border to reach Luohu Shenzhen. There you can walk to reach Luohu Bus Station where you can find direct and frequent buses to reach Qingxi. The buses operate 07:35-20:20 and the interval is around 20 minutes.