I would expect a semi dry method to be good at dealing with a soot clean. Usually the soot is contained in the upper fibres and as you would be able to see a marked difference in the appearance it would be an ideal method. Sponges or sawdust as that is what they really are, also good for soot damaged soft toys. Put them in a large pillow case with the sponges and bung them in the tumble dryer on a cool setting, come out sparkling.