This has nothing to do with the question but what the heck is that one perpendicular beam at the bottom doing besides adding weight the other beams? They didn't even hang the ceiling fan off of it which would have made a little more sense. The load is carried by the load bearing wall anyway.
Way back when I was younger I had a double wide trailer that had a cathedral with beams. In between the beams was that wallpaper sheetrock with those ugly buttons. It looked like a car with three wheels on it. Every week I bought some 1/4" beadboard T&G and when I had enough to do one beam I did it. Took me a year to finish it but I got it done. I was poor as Job's turkey. I clear sealed it before I installed it. I'm not much on tinted stain, I like the natural look. Plus, to me, on the ceiling the lighter the better.