Voicing out of the piano?

[Andrew & Rebeca Anderson]

I'm a little green when it comes to voicing.  What little I do is in 
reaction to undesirable conditions encountered in used pianos.  I usually 
voice in the piano (requires a darn long needle and a lot of saintly 
patience on a grand).

How does one go about voicing out of the grand?  I mean keeping track of 
results, unless you are working with new hammers and intend to treat them 
the same.

Andrew