Bill,  That white glue is a curse to rebuilders.  It works great for
us woodworkers though.  Just the right amount of setup time and great
holding power.

Your removal method is similar to mine.  Just keep scraping and sanding
until it is all removed.  White glues are soluble in weak acid
(vinegar).  A solution of this should remove all traces of the white
glue.  This is essential, as I have found that hot hide glue sticks to
nothing but bare wood.  I only started using hide blue a few years ago.
Properly made, it is wonderful to work with.  Sets up fast with a very
short clamp time.  And if you make a mistake, the joint breaks fairly
easy.

Good luck.

Jim Quashnock