For years I have used a method I discovered while visiting a shop which
does hundreds of keyboards per year for the trade.

Most original key bushings are put in with hide glue (hot animal glue).
You must make a set of felt wedges.  I took a stack of spare new bass
hammers and cut 88 or more wedges out of them.  You can make 6 or 8
wedges from a large bass hammer.  Do not use the center colored felt as
it bleeds color onto the wood.

The wedges should be about 3/4" to 1" long and pointy enough to go 1/4"
or more into the bushed hole.  Soak your wedges in hot water until they
seem to have taken up all the water they can.  This takes 15 minutes or
so the first time.  Thereafter they take up water as soon as you
submerse them.  I clamp all the keys together in 2 or 3 groups just
like they sit in the piano -- usually clamped together by section, so
I can move them all at once.  You can also just lay them out on a table
and do one rail at a time.

When the wedges are wet put one into each hole and let them soak for 10
to 15 minutes.  Sometimes if they did not get wet enough I take a
hypodermic or squeeze bottle of water and drip a few drops on each one.
When they have soaked enough pull each wedge, use a sharp pair of
tweezers to reach in and remove the felt which just lifts out.  If it
takes more than 2 seconds to remove one bushing then they are not wet
enough.  The whole process can take as much as an hour per keyboard
until you get used to it.

Make sure you put the new bushings in with hot glue so the next guy can
get them out easily, too.  Dry out your wedges so they don't sour and
use them on the next piano.  The only possible problem is if someone
used Elmer's glue [casein glue] or if the factory used the white ivory
keytop glue.  Wet wedges won't work easily on Elmer's glue, but the
keytop glue will come out eventually; it just takes more wet time and
sometimes you still have to slice them out.  The white keytop glue is
supposed to be hot glue and whiting, but it makes it more tenacious.

Before I learned this trick, I spent hours and hours scraping out
bushings.  The electric bushing removers never worked very well and
burned the wood half the time.

D. L. Bullock - Piano World - St. Louis - Copyright 1998