Birdsong finishes are not available for sale as a packaged product. You have to send the gun to them to have it applied.
That said, I had a shotgun done earlier this year and the results were amazing. They completely detail stripped the gun, bead blasted it, and finished everything including the springs. They claim you can run the gun completely without lube, and so far my experience seems to refelct that. Granted, it is a pump gun, so it doesn't need much lube anyway.
The Birdsong process actually binds to the metal in a molecular process. I don't think you can really compare it to a spray on, paint-type finish. Apples and Oranges.