Great information about kiln lid flakes from our friends at Paragon...
At Paragon, they coat the inner lid surface of all kilns to reduce brick dust. Sometimes the refractory coating is too thick so, it will blister and flake off when the kiln is fired. An especially thick coating looks like a network of peeling cracks similar to a dried mud puddle. This cracking is due to the difference in expansion between the firebricks and the coating. Conversely, correctly applied kiln coating will look like it disappeared after the kiln has been fired.
First, shake the container very well! Then, pour some of the coating into a bowl. Make sure to stir it just before you apply it to the firebricks. Apply the coating with a large, soft sponge. Moisten the sponge with water; then squeeze out the excess... this is a very important step! Dip the sponge into the bowl of kiln coating. Wipe the coating over the lid surface.
Do not let excess coating run into the element grooves of the kiln. Applying a light coat will prevent this from happening. If the coating drips along the edges of the grooves, remove by wiping a cotton swab or rag along the groove.
The great news is that lid coating lasts for several years. So, it's not something you need to worry about on a daily basis. But, if you start getting kiln brick dust on your work, maybe it's time to re-apply.