If you use pitch put in a little bees wax so it won't be as brittle. It may crack otherwise when it bends.
Beeswax will dissolve in alcohol too, won't it? If animal grease isn't safe with hide glue, I wonder if you could make a wipe-on varnish of wax and pitch. Of course, alcohol isn't primitive. Unless you make your own. But I think that would lead to some legal issues.
Has anybody actually tried animal grease on hide glue? If not, I might do an experimental glue up some time, rub it down with some lard and see what happens...