Thank you all for your comments on stains and oils - I think what I will do is test on several peices of wood to see which outcome I would like best.
So - to get this right - If I powerwash the barn wood, the nice old patina will come off? But if I sand it lightly, it should keep it?
I just want to make sure I keep that rich color look, get a smoother surface, and oil it down.
BUGS - what would the best mothod be to get rid of any hidden bugs in the wood?
In my experience with weathered wood any sanding will leave
raw wood exposed on the high spots, a lighter color and there will plenty of those.
If that's the look you want then sanding will get ya there. I recommended a brush (stiff ) to just remove the crud and loose stuff to keep as much "old wood" look as possible. Your experiments will prove or disprove this. Sand one, brush one, wash with Mineral Spirits which will show the results instantly and kill a few bugs in the process.
Powder post beetles are the main concern since they will find a new source of food and it won't be what you're havin' for dinner. http://www.powderpostbeetles.com/
The choice of finish, oil, poly, water based poly acrylic, is up to you, but I have a laminated oak dining room table with a smooth surface and every year or so I scrub it down with a nylon pad and put an new coat of tung oil or Danish oil and it looks brand new again. The old wood will have crevices and gaps where food may lodge so a poly finish will be easier to clean.
BTW that table looks great if you can achieve that....