Try feathering your brakes as you go downhill, that is compress and release the brakes gently and continuously. If you want to slow down more sit more upright so you are less aeordynamic.
I found downhills very scary on my hybrid bike and I think it was due to the quality of the brakes. When I got a new road bike (which has much better components than the hybrid) I found the braking to be SO much better that I wasn't scared anymore. I'm going to have my bike shop check the brakes on the hybrid and see if I can upgrade.
By the way ... Do you belong to the NY Cycle Club? The people who volunteer to lead rides are very knowledgeable and helpful and could help you out too.