Find any painter with a wholesale license. Get him to go to sherwin-williams and buy the mis mixes. He can take you with him to look. You can buy exterior house paint normally selling for 30 to 40 dollars per gallon for a mere 3.00 per gallon. Any light color will do. Dark colors will absorb too much heat in the summer.
I'm not sure, I haven't tried it. You could go to http://www.beesource.com/forums/index.php and search for this method, then contact those who are doing it. I've heard it said that it really preserves them. I would think it would last longer than painting, would seal the wood better.
I go to the paint stores like Duron, and buy their mis-tints for $3 a gallon. All my nucs used for breeding are different colors. Most of my regular hives are white however as they are requested that way.
Dumpster diving! Oh, yeah!
My farm is next to a municiple/township building and park. Once a year, they have clean up day. Which is a day that you can bring anything to the township, and they will dispose of it. They line up huge trash containers...one for electronics, one for steel scrape, etc. And they allow anyone to hang out and take what they want.
It is amazing what people throw away. I swear that I got bikes because the tire went flat. And at least one lawn mower that needed a spark plug.
Of course I'm always up for some wood for the next bee project.