Roger,

Don Casey wrote an article about this very subject a couple of years
ago. He suggested to wipe the old dorade vents with mineral spirits
and then paint the vents (using a good badger brush) with a linear
polyurethane. I would not use cheap spray paint or automotive paint.
Pettit EasyPoxy or Interlux Brightside are good choices.

Mark A. Bunch, Sr.
Tartan 27 #468 -- "Keeldragger"
http://www.keeldragger.com