Did your brother ever explain why his method works? My uncle does this weird thing with sanding where he uses a damp cloth between coats, and I used to roll my eyes. I mean, idk, maybe it's just me but seeing the smooth finish it gives makes me feel kinda dumb for doubting him.
My grandpa used to wet sand with a drop of dish soap in the water. He said it lifts the grain without scratching, and now I get why those weird tricks work! Makes you appreciate the old school methods.