Invest in a skills clinic to learn proper techniques that would improve all of your riding, not just in the gully, keep you safe, and enable you to have more fun time. Here is why you need to have skills coaching: http://wp.me/p4SBoa-B3
1. IF you don't have a nice dropper post, then drop your seat a little to give yourself more room to move independently of your bike. Sure this will make the climb on the other side more challenging, but hey, it will help keep you safe.
2. Be sure to have a great setup before entering the gully. Ready or attack position, whatever you'd like to call it. Stand up, off the seat, with knees bent outward (not gripping your bike!) Keep your elbow out, back flat, and bend from the hips, with your eyes scanning ahead.Be sure to think ahead, you know, to put that dropper post back up and shift into a lower gear for the abrupt climb.
3. While descending you will adjust your weight back a bit to maintain balance between the front and rear tire. Be sure to keep a slight bend in your arms, and only get back as far as necessary for the slop e of the hill. You also, and should, drop the heel of your forward foot to brace yourself should you need to brake, or hit a bump that brakes for you.
4. On your way up the other side, quickly transition your weight forward in the bottom of the gully. Try pumping this area to gain speed. If you don't know how to pump, there are skills clinics for that too. Keep your weight low and elbows out as you spin up the other side.
You can download a FREE sheet with tips about FUNdamental Skills here: http://wp.me/p4SBoa-Hk