Al,
I'd be surprised if they used water based paint…….The “old” water based (latex) never really got “hard”….The film strength was not comparable to oil based paints.
Now folks like System Three make water based catalyzed Urethanes that work quite well; in the cool/damp New England spring weather these would go on & cure well….That said it's a “thin application” paint and needs multiple coats. Me, I've used Brightside, Easypoxy & Kirby paint – All with good results…. All oil based 2 coats. Pretty simple stuff to work with.