Speaking of primers - I've mentioned this before in other threads, but I'll take the liberty of passing it on again.
During WWII my father was a junior officer on board an attack transport that, though she never came anywhere near the fighting till after it was over, provided Dad with fifty years worth of anecdotes and trivia. One example was his story about primer.
Apparently red lead, which had been the standard, general-purpose primer in the prewar years, was scarce during the war and was used primarily in shipyards for major components of new construction. The primer issued to Navy ships for the standard routine of repainting was a zinc-chromate mixture, which, according to Dad, was a sickly, slightly greenish yellow.
The standard shipboard routine, of course, involved constant scraping and repainting of just about everything. ("If it moves - salute it. If it doesn't move - paint it.") The drill - hour after hour, week after week - consisted of chipping off the old paint (thereby keeping anbody within a 100-foot radius from getting any sleep), brushing on a coat of the primer, letting it dry a few hours, and finally applying the grey (or deck blue, or whatever) finish coat. (Dad recalled that "some of our great geniuses" tried to save themselves some time by mixing the finish coat and the primer. The result was a particularly disgusting green, which the officer in charge made them heave overboard.) Just about every piece of metal on board a ship got that treatment periodically. The only exception was the exterior of the hull, which was off-limits while the ship was under way.
As a result, at any given moment a lot of spots on the ship's interior and exterior would be yellow. The spots would vary in size from a few square inches to a few square feet - and their location would vary by the day or hour.
I once built a model of Dad's ship (U.S.S.
Bollinger, APA-234), based on the old Revell attack transport kit, and gave it to him for Christmas. The look on his face when he put on his bifocals, took a close look at the model, and saw those miniscule yellow spots was something to see.
It's important to make it a dull yellow - and don't overdo it. You should only see the yellow spots if you examine the model carefully. If they're visible at first glance, they're too conspicuous. And they should be in the sort of irregular shapes that would emerge when a gang of none-too-enthusiastic sailors were told to chip the old, loose paint off something.
I've finished a couple of WWII-vintage USN ship models this way, and the yellow dots always get grins of recognition from veterans.