Bernzie: There are a lot of variables when riding in muddy conditions: Tire tread, width, air pressure, tire compound, type of mud. Sometimes the best way to get good at dealing with mud is riding in it and that is not too good on trails. We've had to ride in mud from time to time because it was rain or shine races. Those of us that raced at Canaan and Snowshoe got alot of hands on experience racing in mud because it seemed like it always rained for those races and they were brutal in mud.
On rocks and roots you need to keep the pressure lower and learn to float. The guys from the east explained it to me that it was like snow skiing. On down hills, you use the front tire to stear and the rear tire follows. You slide off course with the front and you've got a crash. The rear tire may slide from side to side but if the front tire is pointing forward and pointing you in the right direction, your generally ok.
Climbing, you have to be able to shift your weight forward and back and know when to weight and unweight the rear tire.
In real muddy races you might see racers actually riding though the wettest area to help clean their tires with water in the ruts. Most riders will gear down and turn higher RPM's. As far as riding faster through muddy areas, I think that's going to depend on your bike handling skills. Muddy courses can be fun and challenging with the right attitude but their hell on equipment and the trails and can be hell on your body too if you crash, especially on rocks! Just my 2 cents.