I dunno about pros, but when I prep a car for a show or a cruise, I spend most of my time cleaning. Just having dirt, dust and road grime removed makes a BIG difference. I usually clean the hoses with lacquer thinner. It doesn't leave them shiny, but clean and "rubber-appearing."
You can use Armorall or other things of that nature (just go to your FLAPS [Friendly Local auto Parts Store...tm Larry Kephart] and you'll see a whole wall of this stuff) but I don't like to spray a buncha that stuff under the hood. Just my preference, but I think it gets WAY overdone.
