There's a very vague line between lacquers and varnishes, that varies with which industry you're involved with and which salesman you're talking to. In some contexts, varnishes are finishes intended to "soak in" and lacquers are intended to make a "layer on top." In other contexts it's just the opposite. Traditional recipes for both consisted of resins and gums dissolved/softened in oils and a solvent, and older versions of both quite frequently used alcohol as the solvent.

Either kind of finish - of "traditional kind" - can be dissolved, or at least softened to the extent of making a "blemish" in the finish, by alcohol and by a number of other "cleaners."

"Modern versions" of both are available that incorporate synthetic "polymers" that (in theory - or sometimes just in the advertising) react chemically when applied to make a more resistant finish. "Harder" finishes are often used on other instruments, but fiddlers tend to be more "tradition-bound" and it is much more likely that fiddle finishes will be readily soluble (and removable) with alcohol.

On the question of rosin on the bow (in this case nothing to do with "Rosin the Beau") my limited experience indicates that with a new or newly-haired bow it's difficult to get the bow to "pick up" enough rosin, until suddenly there's "too much rosin." I have great admiration for those who seemingly always have "just the right amount," and perhaps with enough practice I might eventually achieve that blissful state, but - as previously stated - I'm a non-practicing fiddler - and always have been.

(I have a fiddle - and a banjo - but in my hands they're both used mostly in a manner similar to the common uses of spoons and shaky-eggs. There's a "musical potential" there, but I've not really discovered how to bring it forth. I do better with my 8-string saxophone.)

John