When I restored my player (my first and so far only), I read several
books and info on the internet about removing hide glue.  The general
consensus seems to be that sanding is best. I have to agree with that
for the most part.  But for some parts of a player sanding is not
practical, such as removing the valve pouches and hide glue holding
them in place.

Generally using water is not recommended as it may warp the very dry
and thirsty wooden parts of a player action.  However, I figured that
if I used about as much water at there would be moisture in the amount
of hide glue used to re-glue the part, then there should be very little
if any danger of warping the wood.  I found that if water is used very
sparingly and only applied for a few seconds at a time it can be very
effective in removing hide glue, especially the very thin layer of glue
used on pouches.

Hide glue is very water soluble.  When I applied a small amount of
water to the pouches a few at a time the pouch leather would soak up
the water and melt the hide glue in a mater of seconds.  After that it
was very easy to remove the old pouch - all in one piece.  After
removing the pouch I used a damp cloth the wipe up any remaining water
and hide glue residue.

After removing all of the pouches I went over the pouch board once
more, this time with a wet cloth followed immediately by a damp, almost
dry, cloth to remove the last bit of residue that made everything
sticky.

Following this I used a shop vac to remove any water that may have
deposited on the passages leading to the bottom of the pouch well.
Using a small amount of water on the pouches worked well as there
was no scraping or sanding and as such no changes to the valve stack.

As long as I worked quickly and used the water _very_ sparingly
I didn't have any warpage.  Any longer than a few seconds at a time
and I would see warpage setting to set in.  I let all the parts dry
thoroughly for a few days before doing any re-gluing.  The last thing
I wanted was damp wooden parts sealed up in the valve stack or being
sealed with rubber cloth in the pneumatics.

Of course, as I stated before, I have only restored one player so my
advise may not apply to you.  But using water very sparring to melt
hide glue is something that worked well for me.  I like the fact that
by melting and wiping away the hide I do not introduce any unnecessary
changes (sanding away any shellac or lacquer finishes or deforming the
pouch wells) to the player and have less chance of things not working
right when the player is re-assembled.

Musically,

Ray Finch
Albuquerque, New Mexico, USA