I once used Dow Corning 111 silicone grease to treat a set of
93-year-old pouches that weren't performing well.  They really popped
the valves open quickly after the application, and the piano regained
its snappy performance.

I coat new pouches the same way.  I use the procedure recommended by
Al Pebworth.  Just smear an amount about the size of a match head on
your forefinger (trim back the fingernail before you begin), rub it on
with a circular motion, then take an old T-shirt and, with the same
forefinger, polish the silicone off completely (until there is no more
drag on the cloth).  The pouch gets more limber and is well-sealed.

I find that this process is quicker and more controllable than using
thinned 111.  The sealant stays on the leather but not in it.  I wonder
if a thinning agent allows the sealant to pass into the leather, or if
such an agent would dry out the leather below the sealant, or
compromise the glue at the edge of the pouch.

Use of thinned 111 is a successful procedure, but I prefer Al's rub-on
method.  There are many Dow electrical greases that will work, but 111
seems the most economical and readily available on eBay.

Tim Gautreaux