I've used SMITH'S PENETRATING EPOXY. Clear, it goes on like water, spray it if you like. Very slow cure, penetrates deep into the wood until it finally hardens, then put on some top coat. I like a black marine urethane but probably enamel or anything else you like would work.
The SMITH'S eleminates any chance of dry rot, termites or anything else. I believe it is "SMITH AND CO., RICHMOND,CA"
