No coverage for the marks. Consider one of the keyboard cloth covers.
I had very deep keyboard pattern marks on my Pismo that even appeared to have penetrated to under the LCD's surface. KlearScreen wouldn't touch them. Used one alcohol wipe pad lightly (drugstore variety) and marks were GONE. Completely. Reapplication of KlearScreen made LCD look brand new.
Using alcohol on LCD is not considered a wise choice. Personally, cleaning once or twice a year using alcohol to eliminate those marks seems a reasonable remedy. You also can always dilute the alcohol pad with water until it still removes the keyboard marks, but with lesser alcohol strength.