The first time I helped my dad prep a car for painting I got the glamorous job of wet sanding it by hand. I got done, went in the house and my dad said, "Are you done?"
I got my usual senior high ego in a twist and said, "Of course. It wasn’t that hard." After lunch, my dad went out to look at the car and soon called me over. One guess; do you think it was because I’d done such a good job that no one would ever sand a car again to that quality? Yeah! He ripped me up one side and down the other. I’d missed some places totally and went too deep in others. Then he did something that was embarrassing. He took the sandpaper and block, put them in my hand and with his hand on mine showed me what good sanding looked like. I hated it. It was demeaning. I felt like a fool. But I could probably still sand a car today because his correction gave me the right feel for the amount of pressure needed.