Briefly, practice makes perfect when it comes to desert dune driving.
"Polish comes from the cities; wisdom from the desert" Frank Herbert, American author
Gold rule number 1: Don’t go off-piste by yourself or with just your partner in the vehicle. If you get stuck and its highly likely you will, you could have a long wait before someone shows up to dig you out.
Driving a 4×4 on the sand is a discipline of its own ! There are a few open secrets to maintain a controlled speed while driving at high speed across sand!
Obviously, you are in a powerful 4×4 so make sure you are in 4WD mode!
As you already know, you should really lower your tire air pressure by half or even ⅔. It may look too low to you (ie too flat) but getting the sidewalls to flex out will give you a wider footprint and enable you to 'float' more on the sand. If you choose to only air down to 18 psi, it may not be flat enough, so have faith and air down to the 10 -14 psi range. Once you get stuck your friends can pull you out easier as well.
The choice of additional gear will come with experience. Finding the right tempo while driving ie not too slow or too fast will prevent you from getting stuck in the sand! The more you practice, the more you will be able to anticipate traps while switching gears before reaching rougher areas.
Next point – and I guess I am repeating myself. Go out with friends – because they will get pull you out of a mess when you get stuck. If you are that friend, always pull downhill to get your mate out.
Remember, gravity is your friend. If you say, "but it’s only slightly up hill", you will most likely fail in your mission and get stuck yourself.
Never pull from a tow ball! It can break off and become a deadly projectile!
If your bumper is low hanging, its probably best to take it off before you set off for a day of desert driving; otherwise, you may very well lose it somewhere in the desert.
Next, when you are driving around the dune sideways (with a lot of speed) and you start to slow down, just turn your wheels to point your 4x4 downhill and you will be fine. If you don't point downhill and just stop, you may roll your 4x4.
Automated vehicles are smoother and faster in gear shifting than manual ones.
What to do when you get stuck in the sand ?
As soon as you start to get stuck in the sand, avoid accelerating at that point to prevent from getting even more stuck.
Step out of the vehicle and check how stuck your vehicle is to determine the best solution to get out of the sand while using, if possible, its weight and gravity.
Remove the sand or obstacles around the four wheels.
Remove weight from the car (passengers, bag, water, etc.).
Check the tire pressure and, if possible, reduced it further.
Turn off the air conditioning to put all the power in the wheels.
Switch to low range (or diff-lock) and use the second gear.
Suddenly turn the steering wheel to the right and left to flatten the sand around the wheels and thus increase the grip. Or shake the vehicle from right to left then back and forth to fill the gaps formed by the wheels.
Ask passengers to push the vehicle at the same time while you start it.
Gently start the vehicle.
If despite all these tips you are still stuck, two possibilities remain:
1. Use a board or a sand plate
2. Tow it with a second 4WD
The second 4×4 must be in a safe position (more solid sand, facing downhill…) and both vehicles must be on the same axis.
Tied a tow rope to both vehicles. (Avoid tying two ropes to each other).
Use the hooks, if any. Otherwise, make a solid knot to hang the rope.
Put a piece of clothing on the rope to prevent the rope from coming back if it ever gives way. In any case, passengers need to stay away from both vehicles.
Give both vehicles the coordinated to head toward (find a sign to advance or stop).
Some basic survival tips
If, despite your best efforts, you cant get yourself out of the jam, think twice before leaving your vehicle to seek help. (Perhaps if you do know exactly where to go to seek help and you have enough water to, I guess you could go for it but I wouldn’t recommend it unless you have an injured person onboard and you need urgent medial support).
In most situations, you are in the middle of the desert and you have no idea where you are, so its not a good idea to leave your vehicle!
The desert can be dangerous, and your vehicle will protect you. It is easier to find a car than a single person walking in the desert.
A satellite phone is a very handy piece of kit if desert driving is a passion. In addition, they are easy enough to get in KSA. Youtube is a great resource for how-to video's, check it out before you set off.
The desert offers some amazing sights, experiences and photos opportunities, enjoy it and be safe.