Masts can be built almost independant of the rest of the model. They are fully completed with tops, trucks, half-moons etc. Of course the bowsprit can be considered a mast also.
The masts are only fixed in position when most of the deck and hull detailing is done.
Yards, gafs, and booms are left off, until after some of the standing rigging such as the stays and shrouds have been applied. The image below shows masts at different stages of construction.
It is at this point that the model is finally starting to resemble a TALL ship. The last deck details are created and applied, and an amount of staining, painting and detailing has to be done before we can continue with the next major construction phase: completion of the rigging.
I extensively use airbrushing techniques for large and small surfaces. The thin layers of paint created through airbrushing allow the woodgrain and plank-to-plank edges to remain visible, often adding to the realism of the model.