I’ve had a set of staun deflaters for as long as I can remember and haven’t bothered with anything else.
Local knowledge helps as well - don’t be afraid to ask guys that have been where you are going.
I’ll let them down to 18psi at Fraser Island and have no problems all week generally.
But I know the beaches on the west coast and Tassie for example get heaps of hidden weed and super soft sand as a result so they may use a different psi as their go to.
As said above, letting them down even just a few psi makes a bit difference when it gets hard going, so experimenting doesn’t hurt, and if you’re really struggling 8-10psi helps get out of most things.
And don’t forget if you let them down you need to pump them back up. The number of times some bloke has been stuck and said he didn’t want to let them down any further because he had no way of getting them back up. So get a decent compressor and don’t rely on others.
Same with recovery gear. Get your own and don’t rely on someone else having gear.
But the big thing is if you’re stopped and not going anywhere regardless of pressure, get off the loud pedal and either let your tyre pressure down or use your maxtrax etc. It doesn’t matter what tyre pressure you have, if your body is stuck firmly on the sand to the chassis rails and you’ve dug big holes under your tryes from revving thw crap out of it, you’re going nowhere fast and up for lots and lots of work.
Oh, and sorry if you know all of this, I’m writing for the benefit of a newby, you may not be.