If you want a kind of 'caked on' finish you will need to blend the Kursk Earth with some plaster- this makes it dry fast and gives it some body so it will actually look like deposits of mud.
I use it without the mud aswell to create dusty effects- the way to do it is to apply it straight from the bottle and then wait for a minute or so and then take some thinner on a clean brush and dilute the areas covered in Kursk Earth- try and move the brush in a stippling motion. As you said, you have a piece of scrap, experiment on it and see what you like.
Also check out the
AK Interactive Blog for some helpful hints and tips about how to use their products.
I hope this helps.