Matt,
Guessing that you already have your sag set. I would suggest turrning up the compression dampening on both the forks and the shock. I would turn it up two or three clicks at a time until it felt too stiff and then back it off.
If your rear end starts to feel like it is bucking I would then increase the rebound.
If your bike is under sprung you will notice it in deep sand whoops the most, IMO.
With my last bike I rode a real sandy track and I had the compression maxed out on both ends by the end of the day, and it seemed to help. That was late in the season, and when I serviced the forks in the winter I found the springs were shortened beyond their service limit. I then replaced them and didn't seem to have the same problem the next year.