any idea how to catch a coach or bus to engping from guangzhou?

You mean Enping, do you?
Buses are available in the Provincial Bus Station, Jiaokou Bus Station and Fangcun Bus Station.
If you are in the downtown area, it is suggested to go to the Provincial Bus Station, which is located near the GZ Railway Station. It’s easy for you to find it. More than 20 buses running from 07:00 to 20:10, and the ticket fare is CNY80.