I either soak or dip the parts of my supers, bottom boards and covers in copper napthate under the tradename "coppertox". After that, I let them sit out to dry and air off for probably a day or two. Then, I assemble them with those 2.5inch galvanized nails, and paint the outside with whatever paint I have on hand. Sometimes it's a white semigloss, last time it was old deck paint. The deck paint actually holds up best out of what I've seen. To make them last as long as possible, nail or screw them and put wood glue in the joints. Don't forget to soak the wood in the coppertox and paint the exterior well. That should give them a good, long working life.