a. Great for applying topcoats. Wet your sponge and remove all water then dip into your topcoat. Start applying from one side the other moving across you project. Don't over work or move into the already applied areas. Let dry and repeat.
b. Great for removing water based glazes. Wet your sponge and remove all water. staring in one area remove as much of your glaze as you like. Rinse when dirty and repeat.