Dieseling is caused by too-high idle speed on shutdown, not timing or carbon buildup. A water dribble occasionally won't hurt anything, but I doubt that it will solve the problem. A motorhome 454 won't have the heavy duty parts in it that the tall deck engines have.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!