I started out on a rigid bike in the 90s and was a pretty late convert to front suspension. Now ride a rigid 29er exclusively. I live on Dartmoor so that includes a fair bit of rock and techie stuff.
With the right technique and within reason, you can ride most most stuff rigid that you would on a hardtail or even FS.
Basically you need to be out of the saddle on descents and and be prepared to move your body around a bit to unweight the front end over the rough stuff. Good idea to get comfortable with doing manuals.
You also need to keep it fairly loose - if you're holding the bars in a vulcan death grip, it's going to really hurt after a while and your wrists will get a hammering.
Your arms and legs are going to take the place of the suspension you don't have so you need to flex them accordingly.
As mentioned above, keep your weight well back on descents.
With a bit of practice and enough speed you can effectively unweigh the bike completely and "float" over stuff like small roots and ruts in a zen / ninja stylee.
Enjoy - getting a rigid bike through stuff that everyone else is riding FS will put a huge smile on your face for the rest of the day