But it is also used to refer to coating or finishing a surface with shellack, a kind of varnish.
From the guardian.co.uk
Church and legislative leaders try to shellack their closed-door meetings with a veneer of objectivity.
From the sltrib.com
Then coat it all with shellack and hang it.
From the sltrib.com
More examples
Shellac: cover with shellac; "She wanted to shellac the desk to protect it from water spots"
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes (pictured at right), which are dissolved in denatured alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish. ...
(shellacking) A heavy defeat, drubbing, or beating; used particularly in sports and political contexts
(Shellacking) n. a major defeat or rebuke.
(shellacking) Criticism for a thorough and shameful defeat.
(shellacking) This colorful term was used by President Obama after the Democrats suffered heavy losses in the midterm elections, prompting much discussion about how this slang term came to mean a thorough defeat. I investigated the history of the expression here.