I agree that sand bags aren't a good idea. It can help by putting weight over the drive wheels but once those wheels slip you are more likely to rotate out of control.
Like normal driving it's all about weight transfer and traction. Obviously, traction is reduced in the wet or snow. So you need to be that much more careful transferring weight from wheel to wheel (accelerating, braking, turning). The smoother you can become the easier driving in the snow will be.
In any case, real fast drivers (on the track) are smooth drivers. Start practicing now
