I trained on mine and my families ovens, they got free oven cleans and I got valuablr experience. We must have done over 100 ovens now and have really cut the time down. Main points are warm up to 50deg then apply your cleaner, leave whilst you soak the shelves etc in a dip tank or crate. Scrub with a stinless steel scourer. We also soak the door seal in with the shelves and take the door glass off and soak.
It is really easy once you get the hang of it. A razor blade for scrapping of carbon without damaging the enamel is useful too.