Say you’ve got a Flute with a very shiny finish, not penetrating oil finish, but maybe poly or varnish… how would you bring it down to a matte finish ?
Ben Shaffer
If it were my Flute Ben, I’d get the FINEST grade possible of steel wool and start a rubbin’ 
.If it has some sort of varnish on it,it will come away and leave you with a smooth wooden surface,anxiously awaiting an oiling..
I’d wait and see if any Flute makers/professional woodworkers chime in though,before you start…but thats how I’d aproach things…
If it is an older flute or more recently finished by someone who has a good interest in woodworking, it may be finished with a French Polish or other shellac finish. In that case a good wipe with denatured alcohol would do the trick and would lessen the risk of removing wood where it is needed.
Why?
Because he wants to 
.