We use a hot air gun that is sold for heating and removing paint.
It is much safer than a torch, less odor is produced as you don't need
to scorch the old cloth, and it's quicker and cleaner than using an
iron.

The hot air gun has two settings for the amount of heat, as well as
a nozzle adapter to direct the heat for either a wide or narrow stream
of hot air.  After removing the old bellows cloth, using the gun to
reheat any glue remaining on the boards quickly crystallizes the glue
for easy scraping.  This can be repeated if necessary.

There is little chance of charring the wood with this method.  Then all
that is needed is a light sanding before putting on the new cloth.

Larry Claus