Bill Budenholzer's account of his uncle's recipe is interesting
(thank you!). You can certainly still buy all those ingredients, even
in the UK (some things more restricted than the US), but it seems like
a really, really harsh recipe to me. It might be for a pretty radical
resurfacing that's trying to get something back to a "like new" finish.
Muriatic acid makes it definitely a "gloves and a mask and work
outdoors" job, but even just alcohol and turpentine together will break
down old French polish pretty aggressively.
What I like about shellac and French polish finishes is that it's
not that hard to make a gentle improvement to an old, dirty or damaged
piece without necessarily having to rip off all the signs of age and
patina. Depending on what a piece has been through, a little bit of
fresh shellac polish alone can usually re-amalgamate the surface into
one that will continue to protect the wood and be easy to clean,
without having to eradicate all evidence of age.
To be honest, when I run into old wood I hope it's shellac-polished
so I can do that. If that recipe is for shellac I think it's for the
complete opposite mindset.
I'd love to know what Great Uncle Gus would have done with a cracked,
cloudy, mucky old oil varnish; those seem much more intractable as far
as I'm concerned.