No need to scrub, just put the oven rack in a bag and it will be as good as new.

Luckily, there’s a very quick and fairly natural way to perfectly degrease your oven rack. While it may seem unusual, it’s actually so effective you’ll be surprised.
How to clean it quickly:
First, you’ll need a very large bag, like the ones used for throwing away garbage. The bag must be large enough to hold the oven rack. Next, you’ll need a dishwasher detergent tablet. If you don’t have one, don’t worry, you won’t have to go out and buy one. All you need to do is replace the tablet with a regular laundry detergent.
Next, you’ll need a bowl to place the tablet or detergent. Pour hot water directly onto the tablet in the bowl so the contents dissolve thoroughly. Of course, the water shouldn’t be too hot, otherwise you might puncture the bag. If the tablet hasn’t dissolved completely, you can use a fork to speed up the process.