I recently purchased the Naniwa Pro 5000K - it is slate grey in color and I like the texture and also the results. My question to those of you who have one or have tried one - I cannot seem to keep it wet. I even soaked it before using it to see if that would help. I can squirt water on it and see it soak in before I can make two passes. Is this normal? Should I soak it over night?