What's the best way to clean brass key cauls ?

[Ron Nossaman]

>      Thank you for the ( typically ) kindly response,
> Mr. Nossaman.

And you for your typically disconnected one. Reading your 
posts is like turning over a rock and uncovering something 
that makes me feel sorry for the rock. What I don't understand 
is why rebushing a key in the funkiest of pianos with new 
bushing cloth would leave the caul any more tainted than using 
the same cloth in the same process in the revered Steinway. Is 
there an actual reason for this that mere humans can comprehend?
Ron N