The GUEST describes half of the method I use when cleaning my camp ovens and Bedourie ovens in the bush. Camp ovens (I gather Americans call the Dutch ovens) are cast iron and Bedourie ovens are spun steel and, when trying to remove baked-on gunge the next morning the best method uses a slurry of sand and ashes from the hearth and a bit of elbow grease. The combination of dissolved ash (alkali), residual fat in the oven and grease is, effectively, soap and works a treat. So well in factg that you usually have to oil the surface of the metal to prevent it rusting.

Cheers, Rowan