Has he got a fancy sander?
The sawmill will serve you better, there will be less to sand.
Or smooth it as well as you can and pour that liquid resin over it and it will have a hard surface.
Liquid resin?? Never used it, but it sounds like a wonderful idea. I could do it all by myself except getting those big rocks out of the riverbed. I think you have been a genius with your suggestions. Wish you could join me on my benches down by the river this summer