Robbbbb--Do you ice skate? If not, then it is difficult to analogize for you. If you do, however, the body dynamics can feel exactly the same way. For instance, if you ice skate, imagine doing a hockey stop. It's the same type of hockey stop you would accomplish on skis However, rather than keeping your shoulders constantly perpendicular to the fall line (or skates, if your skating), subtely change two things about your body position:
1) do not edge as aggressively as you would in a hockey stop.
2) allow the momentum of your stop to gradually turn your shoulders
At the end of this, you would have completed what my seven year old calls a "J Turn." You will also be facing up hill. Now, just let gravity take you down the hill, but continue to use the shape of your skis to make slow, gentle turns. To go back forward, reverse the dynamics of the J turn. Slowly wedge, apply pressure to the inside ede of your downhill ski, release weight from your uphill ski, let gravity and momentum slowly swing your shoulders back around. Now you're facing downhill.
Though brusquely put, I do somewhat agree with the post above that suggested you might want to master (or at least feel comfortable with) the rudimentary aspects of downhill skiing so that you don't endanger yourself and those around you by going backwards (because, remember, you can't see behind you).