Paste of baking soda and hot water applied to grime. Smear over surfaces with your hand. Next morning, dip some very hot water over the paste areas and scrub. May require 2nd application. Caked on grime may require use of a stiff , hard plastic spatula, used at an angle to lift grime/baked on foods.
that doesn't work very well
Vinegar and baking soda is what I use.
In a cold oven, place a glass dish with half a cup of full-strength ammonia. On the rack under that place a bowl or boiling water. Close the oven and let it stand overnight. The next day the grime on the oven walls should be loosened sufficiently to be easily wiped away with the ammonia what set in the oven over night. Wipe with a clean damp sponge and you are done.