In most applications while using a kiln there is a change you will drop particles on you new kiln floor of on the kiln shelf. Kiln wash protects your investment. When applied if you accidently drop enamel on it it is easy to scrape off. Always reapply.
Kiln wash comes in a powder form. Just add a small amount of water and paint on. Let it dry over night and you are ready to play in the am. Do not dry kiln wash by heating up your kiln, it will flake off.