When I was young, the professionals aboard the various yachts would do the varnish during the winter in the Caribbean. They would go to a deserted island or the back side of an island, in the lee, where there was no dust or pollution in the air. They would never consider doing varnish in New England.
Other boats, it was a winter project in a shed. Over the last 25 years it is the Jamaicans who travel the circuit, coming north in the summer to work and returning home in the winter to work. Now is now completely commonplace. They work steadily with a smile and quick wit.