I’ve been doing this to a lot of my old barnwood and made some furniture for indoors that always turns out beautiful.

I’m using a 100 grit sandpaper pad (you can use 80-120 grit and still be okay in my opinion) for the first sanding. Then finish it with the MINWAX Polycrilic. Let it dry then sand it again with a 220 grit pad. Then hit it with another coat of Polycrilic.

You can use the barnwood outside but you’d need to use an outdoor stain/sealer for it to last.