I've had good luck using Super Glue remover, of all things, to remove
PVC-e glue.  I think there is an alcohol present that softens the glue.
I'm not sure what kind of alcohol, but perhaps that would work even
better.

As the remover works, it turns the glue into a clear, gunky mess that
can be scraped up.  It only works for short time before the glue
reformulates.  Perhaps the alcohol evaporates.

Try doing one valve at a time until you develop a rhythm.  Expect
to go over them more than once, until you are satisfied with the
cleanliness.  Expect also to make a mess.  Have a rag handy that you
can wipe your scraper on and then throw away.  Remover is benign when
it comes to other glues and finishes it may contact.  Try a small area
though, if you're not sure.  Remember, I'm talking about Super Glue
remover, not Super Glue itself!

I use an Ungar heat gun for this kind of work.  It's small and light,
with a nozzle about 1/2 inch in diameter.  I think it was developed to
use with shrink-wrap tubing and may be found at electronics stores for
do-it-yourselves.  It comes with a nozzle that shrinks the nozzle down
to less than a 1/4 inch diameter.

I hold it in my left (off-) hand and use my scraper in my right hand
to chase the heated, softened glue before it hardens again.  As has
been said before, charring may occur.  The Ungar is more forgiving than
the large guns available everywhere.

Whatever technique is used, take your time.  Remember, you want to end
up with absolutely no leaks.

Jeff Davis, in soon to be drought-ridden Seattle