I have used "Everclear" for thinning shellac or mixing from flakes
used in my piano refinishing.  It is basically pure rectified grain
alcohol, and any liquor store should have it.

I have never bought canned Denatured Alcohol in stores because I never
know how long it has sat on the shelf, increasing the possibly of
getting condensation or other contamination from the metal can in it.

John Rutoskey
Baltimore, Maryland