I buy unfinished birdhouses and I first seal them with Rust-oleum Crystal Clear Enamel Spray.

Then I base coat the birdhouse with Ivory paint from the American Accents Distressing Kit. (my favorite paint)

Then I add the accent colors and lots of flowers.

After they are thoroughly dry I put a few coats of Rust-oleum Crystal Clear Enamel on them so they can be hung outdoors.