I have dealt with this problem for years.  I find that soaking the glue
off with lacquer thinner works rather well.  The problem however, is
when you have metal valve plates screwed down with PVC as the gasket.

If the wood was finished with shellac or lacquer it comes off easier,
but if it is raw wood there can be trouble.  I would suggest in the
case of heavy floating of thick glue over all, perhaps the heat gun
would work with the thinner to clean up.  The heat gun can be used
without scorching the wood along the sides if you cover the scorchable
material with pieces of Formica or cardboard or aluminum foil or metal
sheeting.

You can also use a mere hair dryer rather than the 500-700 degree
Master heat gun we use on the house paint stripping as well as opening
Simplex valves sealed with burned shellac.  Also a big heat gun can be
used for short periods without danger of scorch.  Ampico valve blocks
require 10 seconds in front of a heat gun to remove the metal seats and
some less for Simplex seats.

For removing Hardman Duo seats perhaps folding a cloth saturated in
lacquer thinner and laid down on the area would help.  I would use
a squirt bottle to dribble more thinner on the cloth to keep the area
saturated for 10-20 minutes or more.

Also a good thin blade knife or putty knife might help encourage the
plate to come up.  I have done this with some minor bending among the
seats.  I drill a hole the size of the valve hole in a piece of spare
pin block material, sand it perfectly flat and put the bent seat in
position just like it would be in the stack.  Then use a wide flat
wooden paddle to paddle the seat flat once again on each one that
I bent.  I also put them back on using new blotter paper gaskets.

If resurfacing valves glued with PVC I soak them in lacquer thinner.
If they are plastic fiber disks they can melt if you they are soaked
too long.  In most cases, I would simply use new disks from Organ
Supply Industries and replace all the old ones.  I don't like wasting
time futzing over every little valve disk; I have too much to do.
And customers don't want to wait for you any longer than necessary.

D.L. Bullock    St. Louis
www.thepianoworld.com