Soak soak soak. Fill with enough hot water to cover the burned areas by 1", then bring to a boil. Let stand until it cools, then scrub with a nylon scrub pad. You should be able to remove the crusted-on burnt parts, though the enamel may be stained underneath.

I swear by this method.
http://reviews.ebay.com...

I'd just give it 20 mins for enamelware tho.

Something like this was just asked about a week ago: http://www.food52.com/hotline...

The method I use is just a solution of water and white vinegar. Bring it up to a boil and just scrape away with a wooden tool.

Simmer water for 30 min, wash, rinse and repeat until the burn is gone.