Damage cast iron? Surely you jest! The stuff is tough as woodpecker lips! I use a round toilet bowl brush and a strong solution of Dawn dishwashing liquid, and scrub vigorously for several minutes. When you think the cylinder walls are "clean enough"- - - -do it again!
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!