Interested in Language
The Longman Dictionary of Contemporary English isn't very useful here:Separating facts from rumors is always hard work, especially for a busy parent. And the white noise generated by the experts—to say nothing of the pressure exerted by fellow parents—is so overwhelming that they can barely think for themselves. The facts they do manage to glean have usually been varnished or exaggerated or otherwise taken out of context to serve an agenda that isn’t their own.varnish 2 verb [ transitive ]
to cover something with varnish
However, if you varnish something, you usually do that to improve something. So I'm guessing that if you varnish facts, you make them look better than they actually are.
Is that what is meant by varnish in the quote?
Yes, the "facts" have been made to look better and possibly disguise things that someone doesn't want to be seen.