gee’s route is a pretty good intro and includes most of the well-known trails. If you are driving to the area, you probably dont want to do the big loop to the West of Hound House Lane (although there is a fun trail immediately west of there which is on gee’s GPS track.)
Do a search on Hurtwood Control Car Parks 2, 3 or 10 all would be good places to start that route.
Be mindful that some non-bikers get pissed off with people riding the drop into Car Park 2 so if you want to do that (once you look on a map you can work it out), pls be careful, discrete, dont jump the ditch onto someone’s dog, etc