I've done the toothpaste method also and it works a treat. You wood the following,
2 x think wooly socks
1 x toothpaste
1 x bowl of water
1 x masking tape
First tape around your head light. Then wet the first sock and wash the headlight. With the other sock, apply some toothpaste and rub into the headlight in a circular motion. It will take a lot of elbow grease as the paste dries and gets hard to rub in but the more effort you put in the better the result. Do this for about 10 minutes or so and until the whole headlight is done. When you have have finished, use the first wet sock to wash the headlight.