We have lots of snotty downhills where I ride. Two things I alwasy keep in mind are:
1. Always, always, stand up for balance, using both brakes to control the slide of each end. If you sit you are generally headed for trouble. Don't worry too much about the front sliding as long as you can get the rear to slide the same or faster.
2. Don't get too focused on going slow or trying to maintain the same speed. Instead, maintain balance, control your speed as much as you can but let your speed increase as necessary (let er roll as I say!).
Downhills like that are always tricky (but hugely fun). Cam.