I've found the easiest way is to do it opposite of how you've started.
See Mike Ashey's Kalmbach book Basics of Model Shipbuilding.
First, paint the deck -- all of it, the wood color (do any masking and striping for boards now).
Then go back and mask the deck leaving all the deck fittings exposed. It is labor intensive but results in a good look. Be sure to burnish all the tape down well.
Then go back and spray the fittings. Remove the mask and touch up any overspray with a hand brush (either wood or fitting color).