I'm boondocking in sand right now. Good test is walking. You can feel how soft the sand is by how much effort it takes.
I would put the truck in 2nd gear and be ready to give quite a lot of throttle when you start to feel the resistance of soft sand. It's all about keeping momentum and you need to be very aware of when you start to lose it.
The back axle might start to hop on you. Becomes tricky because you need to let off slightly to stop the hop but you can't let off too much and lose that momentum.
Sometimes you have no choice and have to keep on the gas and just let it hop and shake until you're back on harder ground and can stop and regroup.
Reducing air pressure will help a lot. But its understandable not wanting to. I never do because the sand I'm camping on right now is hard enough that we dont sink. My friends who camp on soft sand drop their trucks and trailers to 10-15psi.
