OK, I do clean off the grates and sometimes some Grease Lightning on the floor, but the walls and outside........nada.
I have a chargriller with SFB. I only clean the grates. I foil the inside under the grates and just throw away the foil and wipe the excess grease with some paper towel. The top half has a nice glossy black patina that doesn't come off on your fingers when you rub it. It's like enamel now.
I take the grates out and brush them with a brass brush and soap and water. The main section of my RF gets the rf plate area scraped with a bondo spreader. I then heat it to 250+ and hose some water in, close the door, let it steam and drain. Repeat if necessary. Let it warm up again to dry.