I do the lettering last (after doing the gold and clear coat) using
black key paint sold by the piano suppliers for the purpose of renewing
the black on the sharp keys.  The paint is fairly thick and therefore
easily controllable with a brush.

I use an artist brush that I've trimmed the bristles rather short
for better control.  I just take my time applying it, and if I make
a mistake, I clean off the error immediately with a cotton swab dampened
in paint thinner, allow to dry, and redo it.

The raised letters in the casting actually help guide the brush pretty
well, and the process isn't all that difficult -- it just takes some
patience and time.

John Runge