Been there and looooooved it.
They will tell you what tire pressure to go to, but I ended up with around 0.6 to 0.8 bar. That was perfect especially in the latter part of the trip.
You will quickly learn what your Paj will do in 2H

4H, 4HLC and 4LLC.
From my memory the smaller dunes, long stretches of sand 4H is good enough. Somewhat larger dunes 4HCL (you need power on the front the front wheels) and the very large dunes in 4LLC. But then, play, thats what you going for.
I only got stuck once

when I turned to sharp and pushed my front left off the rim. That was it and stuck..... So watch the sharp turns.
The 3.2 DiD has enough Umpfff and is not scared. The nice thing on this trip is that it starts off slow and gentle (assuming you doing the Lüderitz to Walvis one) and gets bigger by the day.
The most important thing to remember is when you get to the "Langwand" one drives down one moerova steep dune to the sea. TAKE IT EASY WHEN TURNING...... You DO NOT want to push your tire of the rim there. Had a Cruiser on our trip that managed that and it ended up a rather exciting rescue mission fighting against the tide....
Go have fun... See here:
https://www.pajeroclub.co.za/forum/view ... f=37&t=249 There is a pic called "oops", thats when my tire came off the rim...