There are different approaches to environmental sealing. The old standby is to fill the ambient chamber with either silicone grease (piston regs) or silicone oil (diaphragm regs) to transmit the ambient pressure and then contain it with a flexible diaphragm or boot. The downside is that both leak in hot weather and over time. A variant on this is to use alcohol. It does not expand as much with temperature changes but it is more prone to leakage as it is less viscous.
Sherwood uses an air bleed system that for the most part keeps the ambient chamber dry - but it has a small constant leak that will vent a small stream of bubbles under water. And if you descend too fast, the system has to play catch up.
One design out there uses a diaphragm, a schrader valve and some mushroom valves to maintain air in the ambient chamber. It works well, but he complexity is probably not all that desireable on a regulator where the KISS principle is a good idea.
The latest approach is careful design of the ambient chamber, diaphragm and pad to allow a completely sealed dry chamber. It works, is simple and is easy to maintain. it is probably the ebst way to go for a cold water reg.
The other half of a cold water reg is good heat transfer. With a perfectly sealed ambient chamber but poor heat transfer, you run the risk of having abig ball of ice form over the first stage and that can cause a freeflow too due to physical interference with the diaphragm in addition to problems with maintaining the proper IP if the ambient pressure is no longer transmitted to the interior of the reg.
Good cold water technique helps with any reg. Don't supercool the reg by:
1. Checking it prior to the dive in cold weather. If it worked at home, it will still work at the site an hour or two later.
2. Using the power inflator to fill your BC prior to getting in the water.
3. Using the power inflator to fill your dry suit priro to gettign in the water.
In general any use of the reg when it is above water just cools the reg as heat transfer is very poor out of the water (about 80 times less efficient) and if the reg cools below freezing ice will form on it when you enter the water either immediately causing a freeflow or insulating the reg and causing less heat transfer which can cause the reg to freeze flow later in the dive.
Once in the water do not over breathe the regulator and do not let the mouthpiece fallout of your mouth resulting in a freeflow. Do not inhale and inflate at the same time and do not give a long blast on the BC or drysuit inflator - use short bursts a few seconds apart to allow the reg more time to draw heat from the water to offset the adibatic cooling that occurs.
Also, pull back any rubber hose protectors from the metal hose fittings. The extra exposed metal surfaces on the reg significantly improve heat transfer.
I am a pretty new diver myself, so I am still learning too 
