mtbfree's advice is good.
If I'm flying down a hill and hitting sand-over-hardpack at the bottom, and assuming my tires have hope of reaching said hardpack, I'll usually keep my weight balanced on the tires.
Sometimes coasting through is better than pedaling through, especially at speed. Sometimes your front tire slows, and pedaling keeps your back tire moving, and then things go wonky.
Speed control is sometimes better done w/the rear brake, because you don't usually want a weight shift onto the front wheel.
When struggling to pedal through deep sand there is sometimes a point at which you can feel the rear tire bite when you lean your weight back.
Tread makes a difference. I did a 24-mile ride on Friday on some Bontrager XR-1s. Fast tires. Not good in sand. Had to walk a couple of the sand traps.
mtbfree is right on about improvising. You'll get used to it. Michigan offers plenty of opportunity for practice in sand.