Most people attack a dirty oven with a scouring pad and a lot of effort, and still leave streaks of baked-on grease behind. Professionals do the opposite. They let time and chemistry do the heavy lifting, so the actual cleaning takes minutes.
The racks
Take the racks out and soak them overnight in the hottest water you can run, with a scoop of biological washing powder or a degreaser. By morning the softened grease wipes away with almost no scrubbing.
The cavity
Mix bicarbonate of soda with a little water into a spreadable paste. Coat the interior glass and walls and leave it overnight. Keep it off the bare heating elements and the fan. In the morning, wipe it away and it lifts the softened grease with it. For any stubborn residue, spritz with a little vinegar to fizz it loose, then rinse.
One caution
Keep bicarbonate off bare elements, and never take an abrasive pad to self-clean enamel, as it wrecks the coating. Gentle and patient always beats harsh and fast.
A spotless oven interior and door glass is also one of the very first things an inventory clerk opens at check-out, so it is worth getting right. See the full picture in what an inventory clerk checks first.